Question

A river flows with a steady speed v. A student swims upstream a distance d and then back to the starting point.The student can swim at speed c in still water. a) In terms of d,v, and c what time interval is required for the round tip? [I put L/(d-v) + L/(d+v) + L/c dont know if that's correct] b) What time interval would be required if the water were still? Use any variable or symbol stated above necessary. c) Which time interval is larger: swimmng in still water, it will vary, simming with and against the current