Answer
a) Refer to Graph I
b) Domain is {$r$ | $0 \le r \le 3$}, and
the range is {$A$ | $0 \le A \le 9\pi$}
Work Step by Step
a) Refer to Graph I for graphing of the function $A$ = $\pi$$r^2$ with 0 $\le$ $r$ $\le$ 3 (in black color).
b) Domain is {$r$ | $0 \le r \le 3$}, and
the range is {$A$ | $0 \le A \le 9\pi$}