Can anyone help with the last part of the question (aka part b which sould really be part c)? I'm quite stuck and I've finished the first two parts, but the third one doesn't seem to give all the necessary info to solve it

Cheers in advance

Atourist boat is used for sightseeing in a nearby river. the boat travels 2.4 miles downstream and in the same amount of time, it travels 1.8 miles upstream. if the boat travels at an average speed of 21 miles per hour in the still water, find the current of the river.