The base of a basketball goal has the shape of a rectangular pyramid. The base of the goal must be filled with sand so the goal does not fall down. The base of the pyramid is 4.5 feet long and 4 feet wide. The height of the pyramid is 2.5 feet. How much sand will be needed to fill the base of the basketball goal?

A. 7.1 ft^3
B. 15 ft^3
C. 22.5 ft^3
D. 45 ft^3