Alice and Bob play a game involving a circle whose circumference is divided by 20 equally-spaced points. The points are numbered clockwise, from 1 to 20. Both start on point 20. Alice moves clockwise and Bob, counterclockwise. In a turn of the game, Alice moves 6 points clockwise and Bob moves 10 points counterclockwise. The game ends when they stop on the same point. How many turns will this take?
4
5
8
10
20
