A retaining wall with its face inclined at 75° with horizontal is 10 m high and retains soil inclined at a uniform surcharge angle of 10°. If the angle of internal friction of the soil is 36°, wall friction angle 18°, unit weight of soil 15 kN/m3, and a line load of intensity 90 kN per metre run of the wall acts at a horizontal distance of 5 m from the crest, verify the active thrust on the wall by Culmann's method.