A swimmer heads directly across a river, swimming at 1.6 m/s relative to the water. She arrives at a point 40 m down- stream from the point directly across the river, which is 80 m wide. (a) What is the speed of the river current? (b) What is the swim- mer's speed relative to the shore? (c) In what direction should the swimmer head in order to arrive at the point directly opposite her starting point?