Question 6) [30 Marks] What is the order of magnitude of peak shear strength, critical shear strength and residual shear strength? Which of these shear strengths should be used for the design purpose? (Answer in maximum 4 lines) Question 7) [30 Marks] If the water table level behind a retaining wall rises, what is the change on the magnitude of the lateral force acting on the wall and the magnitude of the sliding factor of safety at the base of the wall? (Answer in maximum 3 lines)