You need to break this into pieces. The 2 ends are triangles, so use the triangle formula: 1/2bh
A = 1/2(7)(8)
A = 1/2(56)
A = 28
Then multiply by 2 since there are two ends: 2 * 28 = 56 square inches.
Next is the 3 sides. They are each 16" by 7".
A = 16 * 7
A = 112 square inches.
Then multiply by 3 since there are 3 of them: 112 * 3 = 336
56 + 336 = 392 square inches of surface area.