An amount of solid NH4HS is placed in a flask already containing ammonia gas at a certain temperature and 0.50 atm. pressure. Ammonium hydrogen sulphide decomposes to yield NH3 and H2S gases in the flask. When the decomposition reaction reaches equilibrium, the total pressure in the flask rises to 0.84 atm. The equilibrium constant for NH4 HS decomposition at this temperature is
(a) 0.30
(b) 0.18
(c) 0.17
(d) 0.11
