A block of mass $\sqrt{3} \mathrm{~kg}$ resting on a horizontal surface. A force $F$ is applied on the block as shown in figure. If coefficient of friction between the block be $\frac{1}{2 \sqrt{3}}$ what can be the maximum value of force $F$ so that block does not start moving? (Take $g=10 \mathrm{~ms}^{-2}$ )
(a) $20 \mathrm{~N}$
(b) $10 \mathrm{~N}$
(c) $12 \mathrm{~N}$
(d) $15 \mathrm{~N}$