A = 1
2 × (15 + 20) × 16
B = 1
2 × 15 × 20 × 10
C = 1
2 × (15 + 20) × 10
D = 1
2 × (10 + 16) × 20
![A 1 2 15 20 16 B 1 2 15 20 10 C 1 2 15 20 10 D 1 2 10 16 20 class=](https://us-static.z-dn.net/files/d85/cdf88176db20b5b63b544f60052c51f8.png)