Problem $4$: A wall with a height of $5$ m $.$ The unit weight of the soil is $18\mathrm{.}2k\frac{N}{m^3},$ angle of

internal friction of soil is $30,$ wall friction angle is $20,$ cohesion is $0.$ The backfill is making an

angle of $10$ from the horizontal. The backface of the wall makes an angle of $85$ from the

horizontal.

Compute the Coulomb's active pressure coefficient.

Compute the Coulomb's active per meter length of wall.

Compute the location and direction of the resultant active force.