A Piece of Rectangular Sheet Metal Is 21 Inches Wide

Multiple Choice

A piece of rectangular sheet metal is 21 inches wide. It is to be made into a rain gutter by turning up equal edges to form parallel sides. Let x represent the length of each of the parallel sides. For what value of x will the area of
The cross section be a maximum (and thus maximize the amount of water that the gutter will hold) ? If necessary,
Round to 2 decimal places.

A) 42 in.
B) 84 in.
C) 10.5 in.
D) 5.25 in.