A manufacturer of jet engines estimates that the rate at which maintenance costs are incurred on its engines is a function of the number of hours of operation of the engine. For one engine used on commercial aircraft, the function is r (x) = 60+ 0.040x 2 where x equals the number of hours of operation and operation. r (x) equals the rate at which repairs cost are incurred in dollars per hour of i. Determine the rate at which costs are being incurred after 100 hours of operation. ii. What are the total costs expected to equal during the first 100 hours of operation.