From Mechanics

Friction will "try" and prevent motion that is achieve equilibrium.

\displaystyle \begin{align} & \text{For}\ \text{equilibrium}\ P-F=0 \\ & \text{that}\ \text{is}\ F=760\ \text{N} \\ \end{align}

Also the maximum friction possible is \displaystyle \mu R=0\textrm{.}4\times 1960=784\ \text{N}.

\displaystyle F=760\ \text{N} falls inside this maximum value and thus is the value of the friction.