A vertical wall retaining a soil backfill is shown below. Assign the following quantities to dimensions and soil properties: H1 = 4 ft, H2 = 6 ft, γ above water table = 105 lb/ft3, γsat = 122 lb/ft3, ?' = 30o (both above and below water table), c' = 0, and q = 0. Plot the variation with depth (z) of the at-rest lateral earth pressure behind the wall, and determine the magnitude and location of the at-rest lateral earth force per unit length of wall.