A block $($A$)$ weighing $1$ kN rests on a rough inclined plane whose inclination to the horizontal is $45.$ This block is connected to another block $($B$)$ weighing $3$ kN rests on a rough horizontal plane by a weightless rigid bar inclined at an angle of $30$ to the horizontal as shown in Fig$\mathrm{.}7.$ Find horizontal force $($P$)$ required to be applied to the block $($B$)$ just to move the block $($A$)$ in upward direction. Assume angle of limiting friction as $15$ at all surface where there is sliding. $[$Ans$.1\mathrm{.}8$ KN $].$