11 [ Volume of a cone = 1/3πr^2h] (a) Solid I is a cylinder with a small cylinder removed from its centre, as shown in the diagram. The height of each cylinder is 20 cm and the radius of the small cylinder is r cm. The radius of the large cylinder is 3.5 cm greater than the radius of the small cylinder. The volume of Solid I is 3000 cm^3. (i) Calculate r. (ii) Solid II is a cone with volume of 3000 cm^3. The perpendicular height of the cone is twice its radius. Which solid is the taller and by how much? (b) The diagram shows a triangular prism of length 24 cm. Its cross-section is an equilateral triangle with sides 8 cm. Calculate the total surface area of the prism.