The following parameters are given for a silty clay soil: c$=18$ kPa, $\backslash$phi $=20\backslash$deg $,$ A $=0\mathrm{.}4$ B $=0\mathrm{.}8.$ Find the pore pressures at the beginning and at the end of following stages.

a$)$ Isotropic consolidation at a cell pressure of $200$ kPa,

b$)$ Undrained monotonic axial shear to failure following the consolidation phase with cell pressure raised to $400$ kPa under undrained conditions.