The Marshall County trash incinerator in Norton burns 5 tons of trash per hour and generates 4 kilowatts of electricity per hour. The Marshall County incinerator in Clarksville burns 6 tons of trash per hour and generates 6 kilowatts of electricity per hour. Marshall County needs to burn at least 135 tons of trash each day and generate at least 100 kilowatts of electricity each day. If the Norton incinerator costs $45 per hour to operate and the Clarksville incinerator costs $55 per hour to operate, how many hours should each incinerator operate each day with the least cost to Marshall County? Write an LP for this problem.