#### Answer

a. $450\ ft^2$
b. $450\ ft^2$, see explanations.

#### Work Step by Step

a. Use the table in the exercise. We have $\lim_{x\to15}f(x)=450\ ft^2$
b. Use the graph in the exercise. We have $\lim_{x\to15}f(x)=450\ ft^2$ which is the same as what we get in part-(a). The graph clearly shows that point $(25,450)$ is a maximum of the function, information that might not be obvious from the table.