A boat can move at 5 m/s relative to the water in any direction. A river 300 m wide flows due east at 2 m/s. A dock is located on the opposite bank 400 m downstream (east) from the boat’s starting point. To arrive at the dock in the shortest possible time, the boat should be steered so that its velocity makes an angle θ (measured downstream from the straight-across direction). Which angle is closest to the optimal value of θ?
a) 67∘ downstream
b) 39∘ downstream
c) 23∘ downstream
d) 53∘ downstream