As shown in the figure, a block of mass $$\sqrt 3 $$ kg is kept on a horizontal rough surface of coefficient of friction $${1 \over {3\sqrt 3 }}$$. The critical force to be applied on the vertical surface as shown at an angle 60$$^\circ$$ with horizontal such that it does not move, will be 3x. The value of x will be _________.

[g = 10 m/s²; sin60$$^\circ$$ = $${{\sqrt 3 } \over 2}$$; cos60$$^\circ$$ = $${1 \over 2}$$]