Chemical Equilibrium

The plot of log‌kf versus ‌1∕T for a reversible reaction A(g)⇌P(g) is shown.Pre-exponential factors for the forward and backward reactions are 1015 s−1 and 1011 s−1, respectively. If the value of log‌K for the reaction at 500K is 6 , the value of |log‌kb| at 250K is _________ .
[K=. equilibrium constant of the reaction, kf= rate constant of forward reaction, kb= rate constant of backward reaction ]