what is the surface area of a cube? well the cube has 6 sides all squares (lenght+width)the volume of a cube is just the areas of a side the hieght (or lenght or width since they are equal) so given that the cubes surface area is 3750 sq ft you should be able to find the area of one side then take the square root to find the lenght of one lenght at one edge and use that to find he volume and the answer is 15625 cubic feet
