Chemical Kinetics

Calculate activation energy for a reaction if it's rate doubles when temperature is raised from $20^{\circ} \mathrm{C}$ to $35^{\circ} \mathrm{C}\left(\mathrm{R}=8.314 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}\right)$