The retaining wall is loaded in axial compression and flexure. For the ASD analysis of the wall in part a, shouldn't we use the more complex calculations for 'k' and the moment capacities that takes into accoount the axial loading? In this case the way they used (ignoring the axial load) was ok since the loads were not close to capacity. If the flexure compression stress was closer to the masonry capacity, then the addition of an axial load may make it inadequate, but the method they used would not show that.