A strip footing is founded at a depth 1.5m below the ground surface. The water table is at the ground surface. The footing is supported to carry a net safe load of 400 kN/m^2 with FS = 3. Given Ysat = 20.85 KN/m^3 and phi = 35 degrees, find the required width of the footing using Terzaghi's general shear failure criterion.