Moreover, you have been informed that the following operations happen frequently: Offering a new trip Adding a passenger to a specific trip Removing a passenger from a specific trip Retrieving the average number of passengers per trip of a specified date Displaying all available trips in a format similar to the following: date1: tripNo1 tripNo2 tripNo3 ... date2: tripNo1 tripNo2 tripNo3 ... where dates and trips are sorted in ascending order Saving all the data into a text file