A strip footing foundation $1 \mathrm{~m}$ wide is coestructed in the slope of a hill whose surface inclination is $20^{\circ}$. The scil in the hill is a dense sand, with a usit weight of $19 \mathrm{kN} / \mathrm{m}^3$ and an angle of internal friction of $40^{\circ}$. Assume that the $D N B$ ratio is about 1. Applying a factor of safety of 3. determine the wall looding the foundation can carry, per meter of footing length.