A free gravity retaining wall is to be built in a seismically active region. The wall is considered as an ordinary structure and the allowable outward displacement is equal to dal = 80 mm. It is 3.0 m high with vertical back, a base dimension of 1.4 m and crest dimension of 0.8 m. The wall will be backfilled with sandy gravel, y = 18.0 kN/m, 6 = 35" with a slope of 10% 3.0 m 0.8 m 1.4m B-10 V-18kN/m = 36 Baseball-24 k = 0.15 k, = 0.08 Fig Q1 a) Check that the wall is safe against sliding (ULS = GEO) by calculating the Factor of Safety FS, according to EC7 Design Approach 1. Combination 1. [Make appropriate assumptions for the unit weight of concrete]