The silo shown in a sketch is an air- and water-tight tower. It consist of a lower cylinder surmounted by a frustum of a cone whose lower base is a upper base of the cylinder. The frustum in turn is surmounted by a cupola consisting of a smaller cylinder whose lower base is the upper base of the frustum. This smaller cylinder is topped by a conical roof. The inside radii of the smaller and larger cylinders are 6 ft. and 12 ft., respectively. The altitudes of the frustum and larger cylinder are 6 ft. and 21 ft., respectively. If ensilage can be stored up to the cupola, find the storage capacity of the silo.