A hollow cylinder,open at one end, is constructed of thin sheet metal.The total external surface area of the cylinder is 192pi cm^2.The cylinder has a radius of r cm and a height of h cm.Given that r

A hollow cylinder,open at one end, is constructed of thin sheet metal.The total external surface area of the cylinder is 192pi cm^2.The cylinder has a radius of r cm and a height of h cm.Given that r can vary,(ii) find the value of r for which V has a stationary value (iii) find this stationary value and determine whether it is a maximum or a minimum.