Reaction of the anti-cancer drug cisplatin with water is described by the following Pt(NH3)2Cl2 + H2O -> Pt(NH3)2(H2O)Cl^+ + Cl ^-. The rate of this reaction increase by a factor of 15 on raising the temperature from 25 degreesC to 50 degreesC. What is the activation energy in kJ/mol?