Solve the Problem $A ( x ) = - x ^ { 2 } + 400 x ; \{ x \mid 0 < x < 800 \}$

Multiple Choice

Solve the problem.
-A farmer has 800 yards of fencing to enclose a rectangular garden. Express the area A of the rectangle as a function of the width x of the rectangle. What is the domain of A?

A) $A ( x ) = - x ^ { 2 } + 400 x ; \{ x \mid 0 < x < 800 \}$
B) $A ( x ) = - x ^ { 2 } + 400 x ; \{ x \mid 0 < x < 400 \}$
C) $\mathrm { A } ( \mathrm { x } ) = - \mathrm { x } ^ { 2 } + 800 \mathrm { x } ; \{ \mathrm { x } \mid 0 < \mathrm { x } < 800 \}$
D) $\mathrm { A } ( \mathrm { x } ) = \mathrm { x } ^ { 2 } + 400 \mathrm { x } ; \{ \mathrm { x } \mid 0 < \mathrm { x } < 400 \}$