| Step | Hyp | Ref
 | Expression | 
| 1 |   | ssid 3203 | 
. 2
⊢ 𝐴 ⊆ 𝐴 | 
| 2 |   | fprod2d.2 | 
. . 3
⊢ (𝜑 → 𝐴 ∈ Fin) | 
| 3 |   | sseq1 3206 | 
. . . . . 6
⊢ (𝑤 = ∅ → (𝑤 ⊆ 𝐴 ↔ ∅ ⊆ 𝐴)) | 
| 4 |   | prodeq1 11718 | 
. . . . . . 7
⊢ (𝑤 = ∅ → ∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑗 ∈ ∅ ∏𝑘 ∈ 𝐵 𝐶) | 
| 5 |   | iuneq1 3929 | 
. . . . . . . . 9
⊢ (𝑤 = ∅ → ∪ 𝑗 ∈ 𝑤 ({𝑗} × 𝐵) = ∪
𝑗 ∈ ∅ ({𝑗} × 𝐵)) | 
| 6 |   | 0iun 3974 | 
. . . . . . . . 9
⊢ ∪ 𝑗 ∈ ∅ ({𝑗} × 𝐵) = ∅ | 
| 7 | 5, 6 | eqtrdi 2245 | 
. . . . . . . 8
⊢ (𝑤 = ∅ → ∪ 𝑗 ∈ 𝑤 ({𝑗} × 𝐵) = ∅) | 
| 8 | 7 | prodeq1d 11729 | 
. . . . . . 7
⊢ (𝑤 = ∅ → ∏𝑧 ∈ ∪ 𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷 = ∏𝑧 ∈ ∅ 𝐷) | 
| 9 | 4, 8 | eqeq12d 2211 | 
. . . . . 6
⊢ (𝑤 = ∅ → (∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷 ↔ ∏𝑗 ∈ ∅ ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∅ 𝐷)) | 
| 10 | 3, 9 | imbi12d 234 | 
. . . . 5
⊢ (𝑤 = ∅ → ((𝑤 ⊆ 𝐴 → ∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷) ↔ (∅ ⊆ 𝐴 → ∏𝑗 ∈ ∅ ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∅ 𝐷))) | 
| 11 | 10 | imbi2d 230 | 
. . . 4
⊢ (𝑤 = ∅ → ((𝜑 → (𝑤 ⊆ 𝐴 → ∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷)) ↔ (𝜑 → (∅ ⊆ 𝐴 → ∏𝑗 ∈ ∅ ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∅ 𝐷)))) | 
| 12 |   | sseq1 3206 | 
. . . . . 6
⊢ (𝑤 = 𝑥 → (𝑤 ⊆ 𝐴 ↔ 𝑥 ⊆ 𝐴)) | 
| 13 |   | prodeq1 11718 | 
. . . . . . 7
⊢ (𝑤 = 𝑥 → ∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑗 ∈ 𝑥 ∏𝑘 ∈ 𝐵 𝐶) | 
| 14 |   | iuneq1 3929 | 
. . . . . . . 8
⊢ (𝑤 = 𝑥 → ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵) = ∪
𝑗 ∈ 𝑥 ({𝑗} × 𝐵)) | 
| 15 | 14 | prodeq1d 11729 | 
. . . . . . 7
⊢ (𝑤 = 𝑥 → ∏𝑧 ∈ ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑥 ({𝑗} × 𝐵)𝐷) | 
| 16 | 13, 15 | eqeq12d 2211 | 
. . . . . 6
⊢ (𝑤 = 𝑥 → (∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷 ↔ ∏𝑗 ∈ 𝑥 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑥 ({𝑗} × 𝐵)𝐷)) | 
| 17 | 12, 16 | imbi12d 234 | 
. . . . 5
⊢ (𝑤 = 𝑥 → ((𝑤 ⊆ 𝐴 → ∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷) ↔ (𝑥 ⊆ 𝐴 → ∏𝑗 ∈ 𝑥 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑥 ({𝑗} × 𝐵)𝐷))) | 
| 18 | 17 | imbi2d 230 | 
. . . 4
⊢ (𝑤 = 𝑥 → ((𝜑 → (𝑤 ⊆ 𝐴 → ∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷)) ↔ (𝜑 → (𝑥 ⊆ 𝐴 → ∏𝑗 ∈ 𝑥 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑥 ({𝑗} × 𝐵)𝐷)))) | 
| 19 |   | sseq1 3206 | 
. . . . . 6
⊢ (𝑤 = (𝑥 ∪ {𝑦}) → (𝑤 ⊆ 𝐴 ↔ (𝑥 ∪ {𝑦}) ⊆ 𝐴)) | 
| 20 |   | prodeq1 11718 | 
. . . . . . 7
⊢ (𝑤 = (𝑥 ∪ {𝑦}) → ∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑗 ∈ (𝑥 ∪ {𝑦})∏𝑘 ∈ 𝐵 𝐶) | 
| 21 |   | iuneq1 3929 | 
. . . . . . . 8
⊢ (𝑤 = (𝑥 ∪ {𝑦}) → ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵) = ∪
𝑗 ∈ (𝑥 ∪ {𝑦})({𝑗} × 𝐵)) | 
| 22 | 21 | prodeq1d 11729 | 
. . . . . . 7
⊢ (𝑤 = (𝑥 ∪ {𝑦}) → ∏𝑧 ∈ ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷 = ∏𝑧 ∈ ∪
𝑗 ∈ (𝑥 ∪ {𝑦})({𝑗} × 𝐵)𝐷) | 
| 23 | 20, 22 | eqeq12d 2211 | 
. . . . . 6
⊢ (𝑤 = (𝑥 ∪ {𝑦}) → (∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷 ↔ ∏𝑗 ∈ (𝑥 ∪ {𝑦})∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ (𝑥 ∪ {𝑦})({𝑗} × 𝐵)𝐷)) | 
| 24 | 19, 23 | imbi12d 234 | 
. . . . 5
⊢ (𝑤 = (𝑥 ∪ {𝑦}) → ((𝑤 ⊆ 𝐴 → ∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷) ↔ ((𝑥 ∪ {𝑦}) ⊆ 𝐴 → ∏𝑗 ∈ (𝑥 ∪ {𝑦})∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ (𝑥 ∪ {𝑦})({𝑗} × 𝐵)𝐷))) | 
| 25 | 24 | imbi2d 230 | 
. . . 4
⊢ (𝑤 = (𝑥 ∪ {𝑦}) → ((𝜑 → (𝑤 ⊆ 𝐴 → ∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷)) ↔ (𝜑 → ((𝑥 ∪ {𝑦}) ⊆ 𝐴 → ∏𝑗 ∈ (𝑥 ∪ {𝑦})∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ (𝑥 ∪ {𝑦})({𝑗} × 𝐵)𝐷)))) | 
| 26 |   | sseq1 3206 | 
. . . . . 6
⊢ (𝑤 = 𝐴 → (𝑤 ⊆ 𝐴 ↔ 𝐴 ⊆ 𝐴)) | 
| 27 |   | prodeq1 11718 | 
. . . . . . 7
⊢ (𝑤 = 𝐴 → ∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑗 ∈ 𝐴 ∏𝑘 ∈ 𝐵 𝐶) | 
| 28 |   | iuneq1 3929 | 
. . . . . . . 8
⊢ (𝑤 = 𝐴 → ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵) = ∪
𝑗 ∈ 𝐴 ({𝑗} × 𝐵)) | 
| 29 | 28 | prodeq1d 11729 | 
. . . . . . 7
⊢ (𝑤 = 𝐴 → ∏𝑧 ∈ ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝐴 ({𝑗} × 𝐵)𝐷) | 
| 30 | 27, 29 | eqeq12d 2211 | 
. . . . . 6
⊢ (𝑤 = 𝐴 → (∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷 ↔ ∏𝑗 ∈ 𝐴 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝐴 ({𝑗} × 𝐵)𝐷)) | 
| 31 | 26, 30 | imbi12d 234 | 
. . . . 5
⊢ (𝑤 = 𝐴 → ((𝑤 ⊆ 𝐴 → ∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷) ↔ (𝐴 ⊆ 𝐴 → ∏𝑗 ∈ 𝐴 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝐴 ({𝑗} × 𝐵)𝐷))) | 
| 32 | 31 | imbi2d 230 | 
. . . 4
⊢ (𝑤 = 𝐴 → ((𝜑 → (𝑤 ⊆ 𝐴 → ∏𝑗 ∈ 𝑤 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑤 ({𝑗} × 𝐵)𝐷)) ↔ (𝜑 → (𝐴 ⊆ 𝐴 → ∏𝑗 ∈ 𝐴 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝐴 ({𝑗} × 𝐵)𝐷)))) | 
| 33 |   | prod0 11750 | 
. . . . . 6
⊢
∏𝑗 ∈
∅ ∏𝑘 ∈
𝐵 𝐶 = 1 | 
| 34 |   | prod0 11750 | 
. . . . . 6
⊢
∏𝑧 ∈
∅ 𝐷 =
1 | 
| 35 | 33, 34 | eqtr4i 2220 | 
. . . . 5
⊢
∏𝑗 ∈
∅ ∏𝑘 ∈
𝐵 𝐶 = ∏𝑧 ∈ ∅ 𝐷 | 
| 36 | 35 | 2a1i 27 | 
. . . 4
⊢ (𝜑 → (∅ ⊆ 𝐴 → ∏𝑗 ∈ ∅ ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∅ 𝐷)) | 
| 37 |   | ssun1 3326 | 
. . . . . . . . 9
⊢ 𝑥 ⊆ (𝑥 ∪ {𝑦}) | 
| 38 |   | sstr 3191 | 
. . . . . . . . 9
⊢ ((𝑥 ⊆ (𝑥 ∪ {𝑦}) ∧ (𝑥 ∪ {𝑦}) ⊆ 𝐴) → 𝑥 ⊆ 𝐴) | 
| 39 | 37, 38 | mpan 424 | 
. . . . . . . 8
⊢ ((𝑥 ∪ {𝑦}) ⊆ 𝐴 → 𝑥 ⊆ 𝐴) | 
| 40 | 39 | imim1i 60 | 
. . . . . . 7
⊢ ((𝑥 ⊆ 𝐴 → ∏𝑗 ∈ 𝑥 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑥 ({𝑗} × 𝐵)𝐷) → ((𝑥 ∪ {𝑦}) ⊆ 𝐴 → ∏𝑗 ∈ 𝑥 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑥 ({𝑗} × 𝐵)𝐷)) | 
| 41 |   | fprod2d.1 | 
. . . . . . . . . 10
⊢ (𝑧 = 〈𝑗, 𝑘〉 → 𝐷 = 𝐶) | 
| 42 | 2 | ad2antrr 488 | 
. . . . . . . . . 10
⊢ (((𝜑 ∧ (𝑥 ∈ Fin ∧ ¬ 𝑦 ∈ 𝑥)) ∧ (𝑥 ∪ {𝑦}) ⊆ 𝐴) → 𝐴 ∈ Fin) | 
| 43 |   | fprod2d.3 | 
. . . . . . . . . . 11
⊢ ((𝜑 ∧ 𝑗 ∈ 𝐴) → 𝐵 ∈ Fin) | 
| 44 | 43 | ad4ant14 514 | 
. . . . . . . . . 10
⊢ ((((𝜑 ∧ (𝑥 ∈ Fin ∧ ¬ 𝑦 ∈ 𝑥)) ∧ (𝑥 ∪ {𝑦}) ⊆ 𝐴) ∧ 𝑗 ∈ 𝐴) → 𝐵 ∈ Fin) | 
| 45 |   | fprod2d.4 | 
. . . . . . . . . . 11
⊢ ((𝜑 ∧ (𝑗 ∈ 𝐴 ∧ 𝑘 ∈ 𝐵)) → 𝐶 ∈ ℂ) | 
| 46 | 45 | ad4ant14 514 | 
. . . . . . . . . 10
⊢ ((((𝜑 ∧ (𝑥 ∈ Fin ∧ ¬ 𝑦 ∈ 𝑥)) ∧ (𝑥 ∪ {𝑦}) ⊆ 𝐴) ∧ (𝑗 ∈ 𝐴 ∧ 𝑘 ∈ 𝐵)) → 𝐶 ∈ ℂ) | 
| 47 |   | simplrr 536 | 
. . . . . . . . . 10
⊢ (((𝜑 ∧ (𝑥 ∈ Fin ∧ ¬ 𝑦 ∈ 𝑥)) ∧ (𝑥 ∪ {𝑦}) ⊆ 𝐴) → ¬ 𝑦 ∈ 𝑥) | 
| 48 |   | simpr 110 | 
. . . . . . . . . 10
⊢ (((𝜑 ∧ (𝑥 ∈ Fin ∧ ¬ 𝑦 ∈ 𝑥)) ∧ (𝑥 ∪ {𝑦}) ⊆ 𝐴) → (𝑥 ∪ {𝑦}) ⊆ 𝐴) | 
| 49 |   | simplrl 535 | 
. . . . . . . . . 10
⊢ (((𝜑 ∧ (𝑥 ∈ Fin ∧ ¬ 𝑦 ∈ 𝑥)) ∧ (𝑥 ∪ {𝑦}) ⊆ 𝐴) → 𝑥 ∈ Fin) | 
| 50 |   | biid 171 | 
. . . . . . . . . 10
⊢
(∏𝑗 ∈
𝑥 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑥 ({𝑗} × 𝐵)𝐷 ↔ ∏𝑗 ∈ 𝑥 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑥 ({𝑗} × 𝐵)𝐷) | 
| 51 | 41, 42, 44, 46, 47, 48, 49, 50 | fprod2dlemstep 11787 | 
. . . . . . . . 9
⊢ ((((𝜑 ∧ (𝑥 ∈ Fin ∧ ¬ 𝑦 ∈ 𝑥)) ∧ (𝑥 ∪ {𝑦}) ⊆ 𝐴) ∧ ∏𝑗 ∈ 𝑥 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑥 ({𝑗} × 𝐵)𝐷) → ∏𝑗 ∈ (𝑥 ∪ {𝑦})∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ (𝑥 ∪ {𝑦})({𝑗} × 𝐵)𝐷) | 
| 52 | 51 | exp31 364 | 
. . . . . . . 8
⊢ ((𝜑 ∧ (𝑥 ∈ Fin ∧ ¬ 𝑦 ∈ 𝑥)) → ((𝑥 ∪ {𝑦}) ⊆ 𝐴 → (∏𝑗 ∈ 𝑥 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑥 ({𝑗} × 𝐵)𝐷 → ∏𝑗 ∈ (𝑥 ∪ {𝑦})∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ (𝑥 ∪ {𝑦})({𝑗} × 𝐵)𝐷))) | 
| 53 | 52 | a2d 26 | 
. . . . . . 7
⊢ ((𝜑 ∧ (𝑥 ∈ Fin ∧ ¬ 𝑦 ∈ 𝑥)) → (((𝑥 ∪ {𝑦}) ⊆ 𝐴 → ∏𝑗 ∈ 𝑥 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑥 ({𝑗} × 𝐵)𝐷) → ((𝑥 ∪ {𝑦}) ⊆ 𝐴 → ∏𝑗 ∈ (𝑥 ∪ {𝑦})∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ (𝑥 ∪ {𝑦})({𝑗} × 𝐵)𝐷))) | 
| 54 | 40, 53 | syl5 32 | 
. . . . . 6
⊢ ((𝜑 ∧ (𝑥 ∈ Fin ∧ ¬ 𝑦 ∈ 𝑥)) → ((𝑥 ⊆ 𝐴 → ∏𝑗 ∈ 𝑥 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑥 ({𝑗} × 𝐵)𝐷) → ((𝑥 ∪ {𝑦}) ⊆ 𝐴 → ∏𝑗 ∈ (𝑥 ∪ {𝑦})∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ (𝑥 ∪ {𝑦})({𝑗} × 𝐵)𝐷))) | 
| 55 | 54 | expcom 116 | 
. . . . 5
⊢ ((𝑥 ∈ Fin ∧ ¬ 𝑦 ∈ 𝑥) → (𝜑 → ((𝑥 ⊆ 𝐴 → ∏𝑗 ∈ 𝑥 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑥 ({𝑗} × 𝐵)𝐷) → ((𝑥 ∪ {𝑦}) ⊆ 𝐴 → ∏𝑗 ∈ (𝑥 ∪ {𝑦})∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ (𝑥 ∪ {𝑦})({𝑗} × 𝐵)𝐷)))) | 
| 56 | 55 | a2d 26 | 
. . . 4
⊢ ((𝑥 ∈ Fin ∧ ¬ 𝑦 ∈ 𝑥) → ((𝜑 → (𝑥 ⊆ 𝐴 → ∏𝑗 ∈ 𝑥 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝑥 ({𝑗} × 𝐵)𝐷)) → (𝜑 → ((𝑥 ∪ {𝑦}) ⊆ 𝐴 → ∏𝑗 ∈ (𝑥 ∪ {𝑦})∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ (𝑥 ∪ {𝑦})({𝑗} × 𝐵)𝐷)))) | 
| 57 | 11, 18, 25, 32, 36, 56 | findcard2s 6951 | 
. . 3
⊢ (𝐴 ∈ Fin → (𝜑 → (𝐴 ⊆ 𝐴 → ∏𝑗 ∈ 𝐴 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝐴 ({𝑗} × 𝐵)𝐷))) | 
| 58 | 2, 57 | mpcom 36 | 
. 2
⊢ (𝜑 → (𝐴 ⊆ 𝐴 → ∏𝑗 ∈ 𝐴 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝐴 ({𝑗} × 𝐵)𝐷)) | 
| 59 | 1, 58 | mpi 15 | 
1
⊢ (𝜑 → ∏𝑗 ∈ 𝐴 ∏𝑘 ∈ 𝐵 𝐶 = ∏𝑧 ∈ ∪
𝑗 ∈ 𝐴 ({𝑗} × 𝐵)𝐷) |