At a temperature of 700 K, the forward and reverse rate constants for the reaction 2 HI(g)  ⇌ H₂(g) + I₂(g) are k_f = 1.8 x 10^-3 M^-1 s^-1 and k_r = 0.063 M^-1 s^-1. 

(a) What is the value of the equilibrium constant Kc at 700 K? 

(b) Is the forward reaction endothermic or exothermic if the rate constants for the same reaction have values of k_f = 0.097 M^-1 s^-1 and k_r = 2.6 M^-1 s^-1 at 800 K?