A strip footing is to be designed to support a dead load of 500 kN/m and an imposed load of 300 kN/m at a depth of 0.7 m in sand. Characteristic values of the shear strength parameters of the soil are c'= 0, and f' = 400. Determine the required width of the footing if a factor of safety of 3.0 against shear failure is specified when the water table rise to foundation level. The unit weights of sand above and below the water table are 17 kN/m3 and 20 kN/m3, respectively.