A retaining wall with a smooth vertical back, 4.5 m high, retains a dry cohesionless backfill level with the top of the wall. γ = 18.6 kN/m3 and φ = 30°. The backfill carries a uniformly distributed surcharge of 20.6 kN/m2. Verify the magnitude and point of application of the total active thrust per lineal metre of the wall.