Rectangular prism is nothing but cuboid.
Volume of a cuboid = length × breadth × height
Base area = length × breadth
It is given that base area = 24 square feet and
height = 5.25 feet
Now, volume = length × breadth × height
= base area × height
= 24 × 5.25
= 126 cubic feet
Hence, the volume of the rectangular prism is 126 cubic feet.