Question: A polystyrene cup is in the shape of a frustum (the part of a cone between two parallel planes cutting the cone), has top radius 2r, base radius r and height h. The surface area S of such a cup is given by S = 3πr√(r2 + h2) and its volume V by V = 7πr2h/3. If the cup is to hold 200 ml, use a calculator or a computer to estimate the value of r that minimizes its surface area.