Apoliceman cruises (on average) approximately 10 minutes before stopping a car for speeding. 90% of the cars stopped are given speeding tickets with an $80 fine. it takes the policeman an average of 5 minutes to write such a ticket. the other 10% of the stops are for more serious offenses, leading to an average fine of $300. these more serious charges take an average of 30 minutes to process. in the long run, at what rate (in dollars per minute) does he assign fines.