7. In a swim/run race, competitors start at point A, and must swim across a river (to any point on the opposite shore), then run along the shore to the finish at point B. The river is 1 km across, and the finish is 5km downstream from the start. If Olivia can swim 4 km/h and run 10 km/h, determine the route she should take to finish the race as quickly as possible. (5 marks) 5 km . B (finish) 1 km . A (start)