How many components are there and what is the variance- if

Question

Solid ammonium hydrosulphide (NH4HS) is mixed with arbitrary amounts of gaseous NH3 and H2S, forming a three-constituent system of two phases, undergoing the reaction

NH₄HSNH₃ + H₂S.

(a) How many components are there, and what is the variance?

(b) Assuming that the gaseous phase is a mixture of ideal gases, show that

PNH₃PH₂S/PNH₄HS = K.

(c) If solid NH₄HS is placed in an evacuated chamber, how many components are there, and what is the variance?