N2 + 3H2 --> 2NH3

Question

At 25°C (delta)Ho = -92.22 kJ and (delta)So = -198.53 J/K. Using this information, calculate the equilibrium constant for the reaction at 2.43x10^2°C. (R = 8.314 J/K)

Apparently the way I'm doing it is wrong:

I divide 198.53 by 1000 then multiply by 298 to get delta(S). Then I subtract this from delta(H) to get delta(G). Then I multiply 516 with .008314... I take this answer and divide delta(G) by it, then multiply by -1. I take this to the e power... Then I use the equation Kc = (RT)^-n * Kp to get the equilibrium constant. However my answer is still wrong.