A man can row a boat at 5 m/s in still water. He wishes to cross a 50-m-wide river to po...

A man can row a boat at 5 m/s in still water. He wishes to cross a 50-m-wide river to point B, 50 m downstream. If the river flows with a velocity of 2 m/s, determine the speed of the boat and the time needed to make the crossing.