The decomposition of HI(g) is represented by the equation 2HI(g) H2(g) + I2(g) Kc= 64 at 25°C. If the equilibrium concentrations of H2 and I2 at 400°C are found to be [H2] = 5.0x10-4 M and [I2] = 1.4x10-3 M, what is the equilibrium concentration of HI?