Consider a complex reaction taking place in three steps with rate constants \( k_1 \), \( k_2 \) and \( k_3 \) respectively. The overall rate constant \( k \) is given by the expression \(\displaystyle k = \sqrt{\frac{k_1 k_3}{k_2}} \). If the activation energies of the three steps are \( 60 \), \( 30 \) and \( 10 \) \( \text{kJ mol}^{-1} \) respectively, then the overall energy of activation in \( \text{kJ mol}^{-1} \) is ________. (Nearest integer)
