Answer
$P = kπr^2$
Assumptions made are discussed in the "WORK STEP BY STEP" session
Work Step by Step
Assume that the paint is applied in a thin veneer of uniform thickness, so that the quantity of paint to be used is
proportional to the area covered. If P is the amount of paint to be used, $P = kπr^2$. The constant $k$ depends on
physical factors, such as the thickness of the paint, absorption of the wood, etc.
