When 5.1 g of solid NH₄HS is introduced into a two litre evacuated flask at 27$^\circ$C, 20% of the solid decomposes into gaseous ammonia and hydrogen sulphide. The K_p for the reaction at 27$^\circ$C is x $\times$ 10^$-$2. The value of x is _____________. (Integer answer) [Given R = 0.082 L atm K^$-$1 mol^$-$]