For the given retaining wall assume "active" state and find:

a$)$ Total horizontal force in $k\frac{N}{m}$ and its point of application.

b$)$ Assume that after a heavy rain season, the drainage is clogged, causing the water table in the backfill to rise to the surface. Calculate the new total horizontal force, assuming a saturated unit weight of $18k\frac{N}{m^3}$

c$)$ Given that the water table has risen to the surface, assume there is a surcharge of $25k\frac{N}{m^2}$ on the backfill. Calculate the total horizontal force acting on the wall.

Normally consolidated sand $($OCR $=1)$

$=14k\frac{N}{m^3}$

${}^{\text{'}}=30$

$c^{\text{'}}=0$