Answer:
The volume of cuboid is 50 ft³, therefore he remove 50 ft³.
Explanation:
The shape of foundation is a cuboid.
The length is 50 ft, width is 12 inches and depth is 12 inches.
We know that
1 ft = 12 inches
So, the width is 1 ft and depth(height) is 1 ft.
The volume of a cuboid is



Since the volume of cuboid is 50 ft³, therefore he remove 50 ft³.