Equilibrium sets problem PCL5--->PCL3+CL2?

a 1.00 mol sample of phosphorous pentachloride is placed in a 10.0 L reaction flask and allowed to come to equilibrium at 250 C. if the amount of chlorine in the equilibrium mixture is 0.470mol, calculate a)the equilibrium concentration of each gas b)Kc and c) the fraction of PCL5 dissociated. the formula is PCL5---->PCL3+CL2