After 40 years as a gynaecologist

After 40 years as a gynaecologist, John decided he had enough money to retire and take up his real love, auto mechanics. He left his practice, enrolled in auto mechanics school, and studied hard. The day of the final exam came and John worried if he would be able to complete the test with the same proficiency as his younger classmates. Most of the students completed their exam in two hours. John, on the other hand, took the entire four hours allotted. The following day, John was delighted and surprised to see a score of 150% for his exam. John spoke to his professor after class. "I never dreamed I could do this well on the exam. How did I earn a score of 150%?" The professor replied, "I gave you 50% for perfectly disassembling the car engine. I awarded another 50% for perfectly reassembling the engine. I gave you an additional 50% for having done all of it through the muffler."