A strip footing, founded on dense sand (?'p = 35° from direct shear tests and γsat = 17 kN/m3 ), is to be designed to support a vertical load of 400 kN per meter length. Determine a suitable width for this footing for FS = 3. The footing is located 1 m below the ground surface. The groundwater level is 10 m below the ground surface.