Swim it

Lolinsan can swim from nowhere to everywhere (with the current of the empty river) in 40 minutes, or back
(against the current) in 45 minutes. How long does it take him to row from nowhere to everywhere, if he
rows the return trip in 15 minutes? (Assume that the speed of the current and Lolinsan’s swimming and
rowing speeds relative to the current are all constant.) Express your answer in the format mm:ss