I need help solving this exercise step by step, please.

$[7-1]$ A foundation is planned to be built on the soil ground shown in Fig. $7\mathrm{.}1($a$).$ The soil has cohesion $c,$ angle

of internal friction $,$ and the unit weight $.$ While increasing the load on the foundation, slippage occurred

within the soil ground and the ground failed.

Rankine explained the possible representation of failure of soil ground by the movement of four blocks of soil

shown in Fig. $7\mathrm{.}1($b$),$ assuming no friction between the bottom surface of the foundation and the soil. In Fig.

$7\mathrm{.}1($b$),$ the overburden pressure around the foundation was replaced and it is shown as the surcharge load, $q_s$

on the ground surface. Fig. $7\mathrm{.}1($c$)$ only shows the right half of Fig. $7\mathrm{.}1($b$).$ Answer the following questions:

$(1)$ In Fig. $7\mathrm{.}1($c$),$ the soil in area I, which lies just below the foundation load, is assumed to be in the active

failure state $[$Fig$.7\mathrm{.}1($d$)].$ What is the angle ${}_1$ which the line BC of area I makes with the ground surface?

$(2)$ In Fig. $7\mathrm{.}1($c$),$ the soil area II$,$ which has surcharge load, is in the passive failure state as the horizontal

force acting here is larger than the overburden pressure. What is the angle ${}_2$ which the line CD of soil II

makes with the ground surface?