As shown in the figure, the width of the river channel L= 100m, and the velocity increases as the river reaches the center of the river. Assume that the flow velocity is u=0.4x (x is the vertical distance from the river bank, and 0≤x≤f=30-2×. Crossing time t = DVC =10010s =10s.

The average speed of water flow velocity is equal to the water flow velocity at d4. Then u = 0.4× D4 =10m/s, so the displacement along the river bank is x = ut =100m.

So the straight-line distance of AB is s =1002+1002m =1002m =141.4m;

So the answers are: 10, 14 1.4.