Answer
a) 3600 cubic feet
b) 27,000 gallons
Work Step by Step
a) The volume that must be pumped is:
$$ V =40\times 60 \times \frac{18}{12} \\ =3600 \ ft^3$$
b) Converting to gallons:
$$ = 3600 \ ft^3 \times \frac{7.5 \ gallons}{ft^3} \\ = 27,000\ gallons $$
