✔ 最佳答案
四人共菜A:
ABC
ADE
AFG
AHI
9 for A * 8C2 for BC * 6C2 for DE * 4C2 for FG * 2C2 for HI = 9 * 28 * 15 * 6 * 1 = 22680
三人共菜A:
ABC
ADE
AFG
BDF
4 for BDF 給誰 * (9 for A * 8P2 for BC * 6P2 for DE * 4P2 for FG) = 4 * 9 * 56 * 30 * 12
= 725760
各菜二人共:
ABC
ADE
BDF
CEF
9C6 for 菜種 * (6P3 for ABC * 3P2 for DE * 1P1 for F) = 84 * 120 * 6 * 1 = 60480
共有 22680 + 725760 + 60480 = 808920 種不同的點菜法。