9.2 gm of ${\mathrm{N}}_2{\mathrm{O}}_{4\left(\mathrm{g}\right)}$ is taken in a closed one litre vessel and heated till the following equilibrium is reached ${\mathrm{N}}_2{\mathrm{O}}_{4\left(\mathrm{g}\right)}\rightleftharpoons 2{\mathrm{NO}}_{2\left(\mathrm{g}\right)}$. At equilibrium 50% of ${\mathrm{N}}_2{\mathrm{O}}_{4\left(\mathrm{g}\right)}$ is dissociated. What is the equilibrium constant (in mole lit^-1)? (M. wt. of N₂O₄ is 92)