Given the potential one-foot thick slope failure along the circular arc (R = 300 ft, 91.44 m)

Question:

Given the potential one-foot thick slope failure along the circular arc (R = 300 ft, 91.44 m) shown in the sketch and the data in Table 2.14, find the safety factor possible with drawdown of the water table below the failure surface. Slope height is 120 ft (36.6 m); slope angle is 29? and specific weight is about 95pcf (15kN/m3). Cohesion is 367 psf (17.6 kPa) and the angle of internal friction of the material is 16?.