Find the volume of the rectangular prism.
V = lwh
V = (9)(16)(4)
V = 756 ft^3
Convert to cubic yards:
1 ft^3 = 0.037037037 yd^3
756 * 0.037037037 = 28
So there are 28 cubic yards of dirt he needs.
Multiply this to 25 to find the total cost of the dirt:
28 * 25 = 700
So the project will cost $700