100m of angle steel is used to make a rectangular frame with three crossbars in the figure.
a) if the width of the frame is xm, determine an expression for l, the length of the frame in metres, in terms of x.
b) the frame is to be covered by light aluminium sheeting. if the area of this sheeting is Am^2, formulate a rule of A in terms of x.
c) Sketch the graph of A against x stating the axes intercepts and turning point. you will need to consider an appropriate domain.
d) Find the maximum area and the value of x which gives this area.