The Equilibrium Constant K_c for the Reaction PCl₃(g) + Cl₂(g)

The equilibrium constant K_c for the reaction PCl₃(g) + Cl₂(g) ⇄ PCl₅(g)
Is 49 at 230°C. If 0.70 mol of PCl₃ is added to 0.70 mol of Cl₂ in a 1.00-L reaction vessel at 230°C, what is the concentration of PCl₃ when equilibrium has been established?

A) 0.049 M
B) 0.11 M
C) 0.30 M
D) 0.59 M
E) 0.83 M