Consider a complex reaction taking place in three steps with rate constants k₁, k₂ and k₃ respectively. The overall rate constant k is given by the expression $\mathrm{k}=\sqrt{\frac{{\mathrm{k}}_1{\mathrm{k}}_3}{{\mathrm{k}}_2}}$.If the activation energies of the three steps are 60, 30 and 10 kJ mol^–1 respectively, then the overall energy of activation in kJ mol^–1 is ________. (Nearest integer)