There is a piece of 10 mm thick a-iron plate. This plate initially has hydrogen uniformly distributed inside with an initial concentration Co. Assume that there is no hydrogen in the air. The plate is left in the air and the hydrogen concentration varies with the time as follows: 4C 3TTX 97 Dt C(x,t) = sin exp II where / is the thickness of the plate. If we would like to remove 95% of the hydrogen from the plate, how long will it take when the plate is at 25 C? The pre-exponential and activation energy for hydrogen in a-iron are 0.1 mm/s and 13,400 J/mol, respectively.