The speed of a swimmer in still water is
20 m/s. The speed of river water is 10 m/s and
is flowing due east. If he is standing on the
south bank and wishes to cross the river along
the shortest path the angle at which he should
make his strokes w.r.t. north is given by :
(1) 30° west
(2) 0°
(3) 60° west
(4) 45° west