Answer:
2880 in^3
Step-by-step explanation:
The complete question is attached.
The steps can be decomposed into two boxes, one of dimensions: 16 in (width), 20 in (depth) and 6 in (height); and another of dimensions: 8 in (width), 20 in (depth) and 6 in (height). The total space inside the steps is the addition of the volumes of both boxes, that is:
Space = 16*20*6 + 8*20*6 = 2880 in^3
