Write a python program that computes the fuel efficiency of a multi-leg journey. The user will provide the starting odometer reading and then information about a series of legs. For each leg, the user provides the current odometer reading, i.e., at the end of the leg, and the amount of gas used. If the amount of gas entered is 0, that leg should be excluded from the calculation. The user signals the end of the trip by entering -1 for the current odometer. The program should display the miles per gallon (MPG) achieved for each leg and for the entire trip. (The MPG should be rounded to two places after the decimal.)