The plot of $\log k_f$   versus  $\frac{1}{T}$ for a reversible reaction A (g) $\rightleftharpoons$P (g) is shown.

Pre-exponential factors for the forward and backward reactions are ${10}^{15}{s}^{-1}$ and ${10}^{11}{s}^{-1}$, respectively. If  the value of  log K for the reaction at 500 K is 5, the value of $\left|\log k_b\right|$ at 250 K is
[K = equilibrium constant of the reaction

$k_f$  = rate constant of forward reaction
$k_b$  = rate constant of backward reaction]