The rate law for the reaction of ${\text{OH}}^{\text{-}}$  with tert-butyl bromide to form an elimination product in 75% ethanol 25% water at ${\text{30}}^{\text{o}}\text{C}$  is the sum of the rate laws for the  ${\text{E}}_2$ and  ${\text{E}}_1$ reactions: Rate $\text{=7.2}\times {\text{10}}^{-5}$  [tert-butyl bromide] $\left[{\text{HO}}^{\text{-}}\right]+4.0\times {10}^{-5}$ [tert-butyl bromide]
What percentage of reaction takes place by ${\text{E}}_{\text{2}}$ path way when conc. of $\left[{\text{HO}}^{\text{-}}\right]$  is 5.0M.