When 5.1 g of solid NH_4 HS is introduced into a two litre evacuated flask at 27^° C, 20 % of the solid decomposes into gaseous ammonia and hydrogen…

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