A swimmer starts at point A on a straight beach and wants to reach a buoy located 50 m offshore and 80 m down the shoreline from A. The swimmer can run along the beach at 6 m/s and swim at 2 m/s. Let x be the distance (in meters) the swimmer runs along the beach before entering the water (0≤x≤80). Which value of x gives the least possible travel time?
a) 18 m
b) 80 m
c) 62 m
d) 55 m