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?

K=? Z=?