Please help me to solve this exercise step by step.

For the following cases, determine the allowable gross vertical load$-$bearing capacity $(q_a)$ of the foundation. Use

Terzaghi's equation and assume general shear failure in soil.

Use $FS=4$ applied to $(1)$ the gross ultimate bearing capacity $(FS=\frac{q_v}{q_a})$ and $(2)$ the net ultimate bearing capacity

$($FS $\{$:$=\frac{q_u-D_f}{q_a-D_f}).$