A = 8 units
B = 3 units
C = 4 units
The reason why these measures are the same as the measures in the rectangular prism is that a rectangular pyramid is naturally 1/3 the volume of a rectangular prism that has the same altitude, base measures. Here are the formulas to compare.
Formula for Volume of Rectangular Prism= Base x Altitude
Formula for Volume of Rectangular Pyramid = (1/3) x Base x Altitude
