Ornithologists have determined that some species of birds tend to avoid flights over large bodies of water during daylight hours. It is believed that more energy is required to fly over water than over land because air generally rises over land and falls over water during the day. A bird with these tendencies is released from an island that is 5 km from the nearest point B on a straight shoreline, flies to a point C on the shoreline and then flies along the shoreline to its nesting area D. Assume that the bird instinctively choose a path that will minimize its energy expenditure. Points B and D are 13 km apart. If it takes 1.4 times as much energy to fly over water as it does over land, how many kilometers from point B will point C be