Equilibrium Constants!! emergency!

A sample of nitrosyl bromide decomposes by the process 2NoBr (g) (arrows both ways) 2NO (g) + Br2 (g). When equilibrium is reached in a 5,0 liter flask, the following quantities are prestent. Find the equilibrium constant Kc of
3.22g NOBr
3,08g NO
4.19g Br2