The equation for the reaction between two gases, A and B, is:

$${\text{2A(g)}} + {\text{3B(g)}} \rightleftharpoons {\text{C(g)}} + {\text{3D(g)}}$$

When the reaction is at equilibrium at 600 K the concentrations of A, B, C and D are 2, 1, 3 and 2 ${\text{mol}}\,{\text{d}}{{\text{m}}^{ - 3}}$ respectively. What is the value of the equilibrium constant at 600 K?

A.     $\frac{1}{6}$

B.     $\frac{9}{7}$

C.     3

D.     6

D