Example $10\mathrm{.}4$: A line load of $100k\frac{N}{?}$ metre run extends to a long distance. Determine the

intensity of vertical stress at a point, $2$ m below the surface and $($i$)$ directly under the line load,

and $($ii$)$ at a distance of $2$ m perpendicular to the line. Use Boussinesq's theory.