A campground owner has \( 2500 \) m of fencing. He wants to enclose a rectangular field bordering a river, with no fencing along the river. (See the sketch.) Let \( x \) represent the width of the field.
(a) Write an expression for the length of the field as a function of \( x \) . (b) Find the area of the field (area = length \( x \) width) as a function of \( x \) .
(c) Find the value of \( x \) leading to the maximum area.
(d) Find the maximum area. (a) \( \ell ( x ) = \square\)