A cutting 9 m deep is to be excavated in saturated clay of unit weight 19 kN/m3. The design shear strength parameters are cu = 30 kN/ m2 and u = 0. A hard stratum underlies the clay at a depth of 11 m below ground level. Using Taylor’s stability coefficients, determine the slope angle at which failure would occur. What is the allowable slope angle if a factor of safety of 1.2 is specified?