2. Christopher watches a stick float downstream in a river and notices that it moves 15 m [E] in a time of 2.5 x 10^1 s. His friend, John, is starting on the south side of the river and is going to swim across. In still water, John knows that he can swim with a speed of 1.2 m/s, relative to the water. a) What is John's velocity relative to the shore? b) If the river is 1.5 km wide, how long will it take John to cross the river?