A box is constructed out of two different types of metal. The metal for the top and bottom, which are the square, costs $2 per square foot and the metal for the sides cost $5 per square foot. Find the dimensions that minimize cost if the box has a volume of 20 cubic feet.

Apinhole camera is made out of a light-tight box with a piece of film attached to one side and pinhole on the opposite side. the optimum diameter d(in millimeters) of the pinhole can be modeled by d=1.9[ (5.5 x 10^-4) l) ] ^1/2, where l is the length of the camera box (in millimeters). what is the optimum diameter for a pinhole camera if the camera box has a length of 10 centimeters