How to find the value of $K_c$?

This is part of my homework. Given the chemical equation :
$$\ce{Sb2S3\_{(s)} + 3H2\_{(g)} <=>2Sb\_{(s)} + 3H2S\_{(g)}}\text{ }K\_{p}=0,429\text{ at }713\text{K}$$
What is the value of $K\_c$ for the reaction?


I used the formula : $K\_p = K\_c(RT)^{\Delta n}$, but I know that $\Delta n$ considers only the coefficients of the reactants and the products of gas forms, so $\Delta n = 3-3=0 \Rightarrow K\_c=K\_p$? 


Am I right? Thanks for any help!


