$10$ moles of ${\mathrm{A}}_2$ , $15$ moles of ${\mathrm{B}}_2$ and $5$ moles of $\mathrm{A}\mathrm{B}$ are placed in a $2$ litre vessel and allowed the come to equilibrium. The final concentration of $\mathrm{A}\mathrm{B}$ is $10.5\mathrm{ }\mathrm{M}$ ,

${\text{A}}_2\left(\text{g}\right)+{\text{B}}_2\left(\text{g}\right)\stackrel{}{\rightleftharpoons }2\text{AB}\left(\text{g}\right)$

Determine the value of equilibrium constant $\left({\mathrm{K}}_{\mathrm{C}}\right)$ for the reaction.