The figure below shows a frustum of a cone. Match each of the expressions with the quantity it describes. (a) π(r1 + r2)[h2 + (r1 − r2)2]1 /2 the total circumference of the flat circular faces the volume the area of the curved surface (b) 2π(r1 + r2) the total circumference of the flat circular faces the volume the area of the curved surface (c) πh(r12 + r1r2 + r22)/3 the total circumference of the flat circular faces the volume the area of the curved surface