$8-82.$ Determine the horizontal force $P$ that must be applied perpendicular to the handle of the lever at $A$ in order to develop a compressive force of $12$ kN on the material. Each single square$-$threaded screw has a mean diameter of $25$ mm and a lead of $7\mathrm{.}5$ mm $.$ The coefficient of static friction at all contacting surfaces of the wedges is ${}_s=0\mathrm{.}2,$ and the coefficient of static friction at the screw is ${}_s^{\text{'}}=0\mathrm{.}15.$

Probs. $8-81/82$