Answer:
The difference in volume of the two models is

Explanation:
we know that
The volume of a square pyramid is equal to

where
b is the length of the side of the square base
h is the height of the pyramid
step 1
Find the volume of Amy's model
we have


substitute


step 2
Find the volume of Alex's model
we have


substitute


step 3
Find the difference in volume of the two models
