A 10-m-high retaining wall with a vertical back face has a c' φ' soil for backfill material. Properties of the backfill material are as follows: g = 19.1 kN/m3, c = 35.9 kN/m2, and f = 28°. Considering the existence of the tensile crack, determine the Rankine active force, Pa, per unit length of the wall.