I'm having a little trouble with this physics problem. It seems so simple but I am stumped.

A river flows with a uniform velocity v. A
person in a motorboat travels 0.942 km up-
stream, at which time a log is seen floating by.
The person continues to travel upstream for
51.3 min at the same speed and then returns
downstream to the starting point, where the
same log is seen again.
Find the flow velocity of the river. Assume
the speed of the boat with respect to the water
is constant throughout the entire trip. (Hint:
The time of travel of the boat after it meets
the log equals the time of travel of the log.)
Answer in units of m/s.

For this problem, I figured that the log traveled .942 km in the amount of time that the boat took to travel 51.3 min and back. I assumed that it was 53.1*2 min to get back to when the boat first saw the log, but I have no idea how to get the amount of time it took for the boat to go the last .942km. I'm not even sure if it's needed in this problem. Please help!