Consider the Following Gas Phase Reaction at 25°C

Consider the following gas phase reaction at 25°C. N₂(g) + C₂H₂(g) ⇌ 2 HCN(g)
600 mol N₂(g) and 1.750 mol C₂H₂(g) are placed in a 1.000 L vessel and the mixture is allowed to react. At equilibrium, there are 1.587 mol N₂(g) in the mixture. What is Kc for this reaction at 25 °C?

A) 9.8 × 10^-4
B) 9.4 × 10^-3
C) 2.5 × 10^-4
D) 4.7 × 10^-3
E) 6.7 × 10^-5