How many 4’x12’x2′ Styrofoam sheets are required to protect water proofing membrane on a foundation that is 32’x60′ with a waterproofed height of 8 feet?

How many 4’x12’x2′ Styrofoam sheets are required to protect water proofing membrane on a foundation that is 32’x60′ with a waterproofed height of 8 feet?