I am unable to solve for questions a, b, c, and d. Can someone help me?

A campground owner has 900 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. River (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) ((x) = (b) A(x) = (c) First write the expression for the derivative used to find the x value that maximizes area. The x-value leading to the maximum area is (d) The maximum area of the rectangular plot is