Which of the following statements apply (select all correct answers)? a)When the water table rises rapidly above the critical slip surface, the FoS tends to decrease for both drained and undrained conditions. b)Design charts presented in the coursebook can be used to estimate the critical FoS associated with a given slope, which is the highest FoS obtained across a multitude of slip surfaces anticipated. c) Janbu’s stability charts can be used to estimate the FoS against slope failure for both drained and undrained conditions, with and without saturated soils. d) Hoek and Bray’s stability charts can be used to estimate the FoS against slope failure for both drained and undrained conditions, with and without saturated soils. e) The ordinary method of slices can be used to calculate the FoS in drained condition only.