checkInData to store check-in information and journeyData to store journey times and counts.checkIn method to store the customer's ID, station name, and check-in time in checkInData.checkOut method to retrieve the check-in data, calculate the journey time, and update journeyData with the new total time and increment the journey count.getAverageTime method to retrieve the total time and count from journeyData for the given start and end stations, and return the average time by dividing the total time by the count.