This question clearly states that it is a 'find the volume' question.
Given dimensions of the object are :
Length of the object = [tex]40\frac{1}{2}[/tex] inches or 40.5 inches
Depth of the object = 10 inches
Height of the object is = 8 inches
So, the volume becomes = [tex]40.5\times10\times8[/tex] = 3240 cubic inch
Hence, the amount of cement needed is 3240 cubic inches.