In a reaction \( \mathrm{A} + \mathrm{B} \rightarrow \mathrm{C} \), initial concentrations of \( \mathrm{A} \) and \( \mathrm{B} \) are related as \( [\mathrm{A}]_{0} = 8[\mathrm{B}]_{0} \). The half lives of \( \mathrm{A} \) and \( \mathrm{B} \) are \( 10 \, \text{min} \) and \( 40 \, \text{min} \), respectively. If they start to disappear at the same time, both following first order kinetics, after how much time will the concentration of both the reactants be same?