NOW, 12. A strip footing is to be designed to carry a load of 800 kN/m at a depth of 0.7 m in a gravelly sand. The appropriate shear stregnth parameters are c' = 0 and f' = 40°. Determine the width of the footing if a factory of safety of 3 against shear-failure is specified and assuming that the water-lavel may rise to foundation level. Above the water-table, the unit weight of the sand is 17 kN/m³ and below the water-table the saturated unit weight is 20 kN/m³.