The small box is 384inches squared for the volume and the larger box is 2,700 inches squared so if you place the smaller box inside the larger box the room left inside the larger box would be 2,316 inches squared
Using sine law:
9/sinc = 15/sin22
sinc = 9sin22 / 15 = 0.225
so c = sin^-1(0.225) = 12.99 degrees ~~ 13 degrees
if B was required:
B = 180 - C - A ~~ 145
If this is multiple choice im gonna say C