Two observation wells penetrated into a confined aquifer and located 2.5 km apart in the directioin of flow, indicate head of 45 m and 20 m. If the coefficient of permeabilitay of the aquifer is 30 /m day and proposity is 0.25, the time of travel of an inert tracer from one well to another is
416.7 days
500 days
750 days
3000 days