Shortest way to Christina

Author:
user2804
Julian wants to visit his friend Christina. She asked him to bring some milk from the gas station. (1) Julian has almost no gas anymore, which gas station should he choose? (2) Julian has enough gas. Which gas station should he choose when he wants to take the shortest way to Christina? (3) Move the blue point and try to find a shorter way than the green one. Can you find one? Explain your discovery!