It has been found that for a chemical reaction with rise in temperature by 9 K the rate constant gets doubled. Assuming a reaction to be occurring at 300 K, the value of activation energy is found to be ____________ kJ mol^$-$1. [nearest integer]

(Given ln10 = 2.3, R = 8.3 J K^$-$1 mol^$-$1, log 2 = 0.30)