Extracted text: A retaining wall is 7m high, with its back face smooth and vertical. It retains sand with its surface horizontal. Using Rankine's theory, determine active earth pressure at the base when the backfill is a) dry, b) saturated, c) submerged, with water table at the surface. Take y = 18kN/m^3 and o = 30°, Vsat = 2 kN/m^2