Dhan raj and Shanth raj were friends and Dhan raj owned a motorboat, which they normally use in the still waters of a nearby lake. The boat always a steady speed of, say 25-km/ hr in still water.

On one vacation, they both decide to haul this boat to a riverside and do a river cruise from some point A to point B and return to A. The current of the river was say, 10km/hr. Dhan raj said that because the river flowed with a reasonably fast current compared to the boat speed, it will take a longer time to cover the same total distance in the river compared to the lake as there is no current in the lake. He said that they should plan accordingly.

Shanth raj disagreed with him completely. He maintained that though the river had a current, whatever speed they lose while going upstream will get compensated when they come back downstream and after all the distance traveled up and down the stream, whatever may it be is the same.

a) Who is correct?
b) Are both partially correct?
c) Are both wrong?
d) What will the difference in time, if any, will depend on?

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