When 5.1 g of solid $\mathrm{NH}_4 \mathrm{HS}$ is introduced into a two litre evacuated flask at $27^{\circ} \mathrm{C}, 20 \%$ of the solid decomposes into gaseous ammonia and hydrogen sulphide. The $\mathrm{K}_{\mathrm{p}}$ for the reaction at $27^{\circ} \mathrm{C}$ is $\mathrm{x} \times 10^{-2}$. The value of x is $\_\_\_\_$ (Integer answer) [Given $\mathrm{R}=0.082 \mathrm{~L} \mathrm{~atm} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}$ ]