Aperson is swimming in a river with a current that has speed vr with respect to the shore. the swimmer first swims downstream (i. e. in the direction of the current) at a constant speed, vs , with respect to the water. the swimmer travels a distance d in a time tout . the swimmer then changes direction to swim upstream (i. e. against the direction of the current) at a constant speed, vs , with respect to the water and returns to her original starting point (located a distance d from her turn-around point) in a time tin . 1) what is tout in terms of vr, vs, and d, as needed?