For the first order reaction `ArarrB+C` , carried out at `27^(@)C` if `3.8xx10^(-16)%` of the reactant molecules exists in the activated state, the `E_(a)` (activation energy) of the reaction is :
A. `12kJ//mol`
B. `831.4kJ//mol`
C. `100kJ//mol`
D. `88.57kJ//mol`