7. The load, P (in pounds), that can be safely supported by a horizontal beam varies jointly as the product of the width, W (in feet), of the beam and the square of the depth, D (in feet), and inversely as its length, L (in feet). If a beam has a width of 2 feet, a depth of 1 foot and a length of 4 feet, the load it can support is 10 pounds. How much could the beam hold if the beam had a length of 6 feet, a depth of 2 feet, and a width of 3 feet?

The safe load, L, of a wooden beam supported at both ends varies jointly as the width, w, and the square of the depth, d, and inversely as the length, l. A wooden beam 8in. wide, 7in. deep, and 2ft long holds up 27412lb. What load would a beam 5in. wide, 6in. deep, and 18ft. long, of the same material, support? Round your answer to the nearest integer if necessary.

4. The height h of a geometric solid varies directly as the volume V and inversely as the square of the radius r. Find the equation of variation if h = 22.6 cm when r = 54.3 cm and V = 209,300 cm³. Extension: What is the solid?