A Sample of Solid NH₄NO₃ Was Placed in an Evacuated $\rightleftharpoons$

A sample of solid NH₄NO₃ was placed in an evacuated container and then heated so that it decomposed explosively according to the following equation: NH₄NO₃(s) $\rightleftharpoons$ N₂O(g) + 2H₂O(g)
At equilibrium the total pressure in the container was found to be 2.72 atm at a temperature of 500.°C. Calculate K_p.

A) 1.64
B) 0.822
C) 2.98
D) 80.5
E) 0.745