A rectangle has one corner in quadrant I on the graph of
\( y = 16 - x ^ { 2 } \) , another at the origin, a third on the positive
\( y \) -axis, and the fourth on the positive \( x \) -axis. See the figure (top, right). (a) Express the area \( A \) of the rectangle as a function of \( x \) . (b) What is the domain of \( A \) ? (c) Graph \( A = A ( x ) \) . For what value of \( x \) is \( A \) largest?