The product property is the answer. You must add exponents when multiplying those with the same bases.
The board is 6 feet long, and there is 12 inches in a foot. This means the board is 72 inches long. Each piece she cuts is 1/4 (3) inches long. This means if we do 72/3, we see the number of pieces Joanna cuts is 24.
Volume of the box = length ^ 3 = 5^3 = 125 cubic inches
Volume of rectangular prism = length x width x height = 3 x 4 x 18 = 216 cubic inches
Volume of entire sculpture = volume of box + volume of rectangular prism = 125 + 216 = 341 cubic inches.