A reaction takes place in various steps. The rate const, for 1st,2nd,3rd and 5th steps are k1,k2,k3 and k5 resp. The overall rate constant is given by k=k2k3(k1k5)1/2. If activation energy are 40,60,50 and 10 kJ/mole resp. The overall energy of activation (kJ/mole) is: