a small office unit is to contain 600 ft2
of floor space. a simplified model is shown in the
figure.
(a) use an equation to express the length y of the building in terms of the width x.

(b) if the walls cost $100 per running foot, use an equation to express the cost c of the
walls in terms of the width x. (disregard the wall space above the doors and the thickness
of the walls.)
wall space above the door=3'