Johnson canniver has a repair shop. he bought a used lawn mower for $35.00 from a customer. he spent $39.17 on parts to repair the mower. he also painted and polished the mower at a cost of $36.43. he was able to sell the refurbished lawn mower for $155.00. if it took 4.5 hours to do all the work, how much did he earn per hour to the nearest cent?