Best Order to clean with regard to departure times?

Hi, I work in a fleet car/van place. The vehicles come in to the depot overnight between 10pm to 10am the next day. They can turn up in any order, take about a hour to clean and then go back out again. I have to juggle the "cleaning order" to prioritise the vehicles to be ready to go at their departure times. In my example it shows the "coming in" times and the "going out" times. I would like to know which vehicle order to start cleaning in order to meet the departure times. Can someone who know how to go about this please help me.. I'm not any good at this stuff, but any help might save my sanity.. many thanks.. John

Hi Wayne, I'm sorry I used a bad example.. I was just trying to explain my problem.. I will expand. Each clean takes about an hour. Being done in time for the departure is "mission critical". On average there maybe 6 to 7 vehicles to sort out. Lets say 1 turns up 2am and leaves at 6am, so can be done anytime between 2am and 5am (allowing 1 hour to clean). The problem comes when another one turns up at say 2.30am but is due to leave at 4.30am. Under this situation it makes sense to do the 2.30am vehicle first and the do the 2am vehicle afterwards. Now the trouble is when trying to sort the "best order" to clean, so the vehicles are ready to go on time is when there are 6 or 7 vehicles. I should say that we have a list of the "coming in" and "going out" times at the start of the shift. Not sure if my explanation has helped.. can you help me with the formula's etc.. thanks.. John