Handy Mufflers is an auto repair service company and uses time-and-material pricing to prepare their bids to delivery companies. They are currently bidding on a maintenance contract with a company that owns 50 delivery vans and trucks. The service manager estimates each annual service call would require $90 in parts and materials and 4 hours of labour (including fringe benefits) at $15 per hour. Their material loading charge is 30%. If they submit a total bid of $10,000 what is their profit margin per labour hour?

Please provide explanation!