Step | Hyp | Ref
| Expression |
1 | | prssspr 45751 |
. . . . . 6
⊢ ((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑝 ∈ 𝑎) → ∃𝑖 ∈ 𝑉 ∃𝑗 ∈ 𝑉 𝑝 = {𝑖, 𝑗}) |
2 | 1 | ad4ant14 751 |
. . . . 5
⊢ ((((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}}) ∧ 𝑝 ∈ 𝑎) → ∃𝑖 ∈ 𝑉 ∃𝑗 ∈ 𝑉 𝑝 = {𝑖, 𝑗}) |
3 | | simpr 486 |
. . . . . . . . . . . 12
⊢ (((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) → 𝑝 = {𝑖, 𝑗}) |
4 | 3 | adantr 482 |
. . . . . . . . . . 11
⊢ ((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ ((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}})) → 𝑝 = {𝑖, 𝑗}) |
5 | 4 | eleq1d 2823 |
. . . . . . . . . 10
⊢ ((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ ((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}})) → (𝑝 ∈ 𝑎 ↔ {𝑖, 𝑗} ∈ 𝑎)) |
6 | | simpr 486 |
. . . . . . . . . . . . . 14
⊢ ((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ {𝑖, 𝑗} ∈ 𝑎) → {𝑖, 𝑗} ∈ 𝑎) |
7 | | eqeq1 2741 |
. . . . . . . . . . . . . . 15
⊢ (𝑐 = {𝑖, 𝑗} → (𝑐 = {𝑖, 𝑗} ↔ {𝑖, 𝑗} = {𝑖, 𝑗})) |
8 | 7 | adantl 483 |
. . . . . . . . . . . . . 14
⊢
(((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ {𝑖, 𝑗} ∈ 𝑎) ∧ 𝑐 = {𝑖, 𝑗}) → (𝑐 = {𝑖, 𝑗} ↔ {𝑖, 𝑗} = {𝑖, 𝑗})) |
9 | | eqidd 2738 |
. . . . . . . . . . . . . 14
⊢ ((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ {𝑖, 𝑗} ∈ 𝑎) → {𝑖, 𝑗} = {𝑖, 𝑗}) |
10 | 6, 8, 9 | rspcedvd 3586 |
. . . . . . . . . . . . 13
⊢ ((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ {𝑖, 𝑗} ∈ 𝑎) → ∃𝑐 ∈ 𝑎 𝑐 = {𝑖, 𝑗}) |
11 | 10 | adantlr 714 |
. . . . . . . . . . . 12
⊢
(((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ ((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}})) ∧ {𝑖, 𝑗} ∈ 𝑎) → ∃𝑐 ∈ 𝑎 𝑐 = {𝑖, 𝑗}) |
12 | | preq12 4701 |
. . . . . . . . . . . . . . . . 17
⊢ ((𝑥 = 𝑖 ∧ 𝑦 = 𝑗) → {𝑥, 𝑦} = {𝑖, 𝑗}) |
13 | 12 | eqeq2d 2748 |
. . . . . . . . . . . . . . . 16
⊢ ((𝑥 = 𝑖 ∧ 𝑦 = 𝑗) → (𝑐 = {𝑥, 𝑦} ↔ 𝑐 = {𝑖, 𝑗})) |
14 | 13 | rexbidv 3176 |
. . . . . . . . . . . . . . 15
⊢ ((𝑥 = 𝑖 ∧ 𝑦 = 𝑗) → (∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦} ↔ ∃𝑐 ∈ 𝑎 𝑐 = {𝑖, 𝑗})) |
15 | 14 | opelopabga 5495 |
. . . . . . . . . . . . . 14
⊢ ((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) → (⟨𝑖, 𝑗⟩ ∈ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} ↔ ∃𝑐 ∈ 𝑎 𝑐 = {𝑖, 𝑗})) |
16 | 15 | bicomd 222 |
. . . . . . . . . . . . 13
⊢ ((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) → (∃𝑐 ∈ 𝑎 𝑐 = {𝑖, 𝑗} ↔ ⟨𝑖, 𝑗⟩ ∈ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}})) |
17 | 16 | ad3antrrr 729 |
. . . . . . . . . . . 12
⊢
(((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ ((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}})) ∧ {𝑖, 𝑗} ∈ 𝑎) → (∃𝑐 ∈ 𝑎 𝑐 = {𝑖, 𝑗} ↔ ⟨𝑖, 𝑗⟩ ∈ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}})) |
18 | 11, 17 | mpbid 231 |
. . . . . . . . . . 11
⊢
(((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ ((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}})) ∧ {𝑖, 𝑗} ∈ 𝑎) → ⟨𝑖, 𝑗⟩ ∈ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}}) |
19 | 18 | ex 414 |
. . . . . . . . . 10
⊢ ((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ ((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}})) → ({𝑖, 𝑗} ∈ 𝑎 → ⟨𝑖, 𝑗⟩ ∈ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}})) |
20 | 5, 19 | sylbid 239 |
. . . . . . . . 9
⊢ ((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ ((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}})) → (𝑝 ∈ 𝑎 → ⟨𝑖, 𝑗⟩ ∈ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}})) |
21 | | eleq2 2827 |
. . . . . . . . . . 11
⊢
({⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}} → (⟨𝑖, 𝑗⟩ ∈ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} ↔ ⟨𝑖, 𝑗⟩ ∈ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}})) |
22 | 21 | ad2antll 728 |
. . . . . . . . . 10
⊢ ((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ ((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}})) → (⟨𝑖, 𝑗⟩ ∈ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} ↔ ⟨𝑖, 𝑗⟩ ∈ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}})) |
23 | 13 | rexbidv 3176 |
. . . . . . . . . . . . 13
⊢ ((𝑥 = 𝑖 ∧ 𝑦 = 𝑗) → (∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦} ↔ ∃𝑐 ∈ 𝑏 𝑐 = {𝑖, 𝑗})) |
24 | 23 | opelopabga 5495 |
. . . . . . . . . . . 12
⊢ ((𝑖 ∈ V ∧ 𝑗 ∈ V) → (⟨𝑖, 𝑗⟩ ∈ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}} ↔ ∃𝑐 ∈ 𝑏 𝑐 = {𝑖, 𝑗})) |
25 | 24 | el2v 3456 |
. . . . . . . . . . 11
⊢
(⟨𝑖, 𝑗⟩ ∈ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}} ↔ ∃𝑐 ∈ 𝑏 𝑐 = {𝑖, 𝑗}) |
26 | | eqtr3 2763 |
. . . . . . . . . . . . . . . . . . . . 21
⊢ ((𝑝 = {𝑖, 𝑗} ∧ 𝑐 = {𝑖, 𝑗}) → 𝑝 = 𝑐) |
27 | 26 | equcomd 2023 |
. . . . . . . . . . . . . . . . . . . 20
⊢ ((𝑝 = {𝑖, 𝑗} ∧ 𝑐 = {𝑖, 𝑗}) → 𝑐 = 𝑝) |
28 | 27 | eleq1d 2823 |
. . . . . . . . . . . . . . . . . . 19
⊢ ((𝑝 = {𝑖, 𝑗} ∧ 𝑐 = {𝑖, 𝑗}) → (𝑐 ∈ 𝑏 ↔ 𝑝 ∈ 𝑏)) |
29 | 28 | biimpd 228 |
. . . . . . . . . . . . . . . . . 18
⊢ ((𝑝 = {𝑖, 𝑗} ∧ 𝑐 = {𝑖, 𝑗}) → (𝑐 ∈ 𝑏 → 𝑝 ∈ 𝑏)) |
30 | 29 | ex 414 |
. . . . . . . . . . . . . . . . 17
⊢ (𝑝 = {𝑖, 𝑗} → (𝑐 = {𝑖, 𝑗} → (𝑐 ∈ 𝑏 → 𝑝 ∈ 𝑏))) |
31 | 30 | com13 88 |
. . . . . . . . . . . . . . . 16
⊢ (𝑐 ∈ 𝑏 → (𝑐 = {𝑖, 𝑗} → (𝑝 = {𝑖, 𝑗} → 𝑝 ∈ 𝑏))) |
32 | 31 | imp 408 |
. . . . . . . . . . . . . . 15
⊢ ((𝑐 ∈ 𝑏 ∧ 𝑐 = {𝑖, 𝑗}) → (𝑝 = {𝑖, 𝑗} → 𝑝 ∈ 𝑏)) |
33 | 32 | rexlimiva 3145 |
. . . . . . . . . . . . . 14
⊢
(∃𝑐 ∈
𝑏 𝑐 = {𝑖, 𝑗} → (𝑝 = {𝑖, 𝑗} → 𝑝 ∈ 𝑏)) |
34 | 33 | com12 32 |
. . . . . . . . . . . . 13
⊢ (𝑝 = {𝑖, 𝑗} → (∃𝑐 ∈ 𝑏 𝑐 = {𝑖, 𝑗} → 𝑝 ∈ 𝑏)) |
35 | 34 | adantl 483 |
. . . . . . . . . . . 12
⊢ (((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) → (∃𝑐 ∈ 𝑏 𝑐 = {𝑖, 𝑗} → 𝑝 ∈ 𝑏)) |
36 | 35 | adantr 482 |
. . . . . . . . . . 11
⊢ ((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ ((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}})) → (∃𝑐 ∈ 𝑏 𝑐 = {𝑖, 𝑗} → 𝑝 ∈ 𝑏)) |
37 | 25, 36 | biimtrid 241 |
. . . . . . . . . 10
⊢ ((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ ((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}})) → (⟨𝑖, 𝑗⟩ ∈ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}} → 𝑝 ∈ 𝑏)) |
38 | 22, 37 | sylbid 239 |
. . . . . . . . 9
⊢ ((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ ((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}})) → (⟨𝑖, 𝑗⟩ ∈ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} → 𝑝 ∈ 𝑏)) |
39 | 20, 38 | syld 47 |
. . . . . . . 8
⊢ ((((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) ∧ ((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}})) → (𝑝 ∈ 𝑎 → 𝑝 ∈ 𝑏)) |
40 | 39 | expimpd 455 |
. . . . . . 7
⊢ (((𝑖 ∈ 𝑉 ∧ 𝑗 ∈ 𝑉) ∧ 𝑝 = {𝑖, 𝑗}) → ((((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}}) ∧ 𝑝 ∈ 𝑎) → 𝑝 ∈ 𝑏)) |
41 | 40 | rexlimdva2 3155 |
. . . . . 6
⊢ (𝑖 ∈ 𝑉 → (∃𝑗 ∈ 𝑉 𝑝 = {𝑖, 𝑗} → ((((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}}) ∧ 𝑝 ∈ 𝑎) → 𝑝 ∈ 𝑏))) |
42 | 41 | rexlimiv 3146 |
. . . . 5
⊢
(∃𝑖 ∈
𝑉 ∃𝑗 ∈ 𝑉 𝑝 = {𝑖, 𝑗} → ((((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}}) ∧ 𝑝 ∈ 𝑎) → 𝑝 ∈ 𝑏)) |
43 | 2, 42 | mpcom 38 |
. . . 4
⊢ ((((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}}) ∧ 𝑝 ∈ 𝑎) → 𝑝 ∈ 𝑏) |
44 | 43 | ex 414 |
. . 3
⊢ (((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}}) → (𝑝 ∈ 𝑎 → 𝑝 ∈ 𝑏)) |
45 | 44 | ssrdv 3955 |
. 2
⊢ (((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) ∧ {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}}) → 𝑎 ⊆ 𝑏) |
46 | 45 | ex 414 |
1
⊢ ((𝑎 ⊆ (Pairs‘𝑉) ∧ 𝑏 ⊆ (Pairs‘𝑉)) → ({⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑎 𝑐 = {𝑥, 𝑦}} = {⟨𝑥, 𝑦⟩ ∣ ∃𝑐 ∈ 𝑏 𝑐 = {𝑥, 𝑦}} → 𝑎 ⊆ 𝑏)) |