Answer:
990, C
Step-by-step explanation:
The formula for the surface area of the bottom cushion is
A = 2wl + 2lh + 2hw (w is width, l is length, h is height)
w = 18, l = 21, h = 3
A = 2(18)(21) + 2(21)(3) + 2(3)(18)
A = 2(378) + 2(63) + 2(54)
A = 756 + 126 + 108
A = 990 (C)
