Answer:
16
Explanation:
The dimensions of the base of the prism are 4" by 2"; the height is 2".
Looking at the base, we see that (4)(2), or (8) 1" cubes would cover it exactly and wholly. We'd have a 3-dimensional prism with one layer of 1" cubes.
Now if we add a second layer right on top of the first layer, we'd have used (16) 1" cubes.