Auto Shop Final Exam

There was a gynecologist who was pretty burned out with his choice of
profession, (it's not all supermodels ya know) So he decides to turn
his hobby of fixing cars into his new career.  Well inorder to become a
licensed mechanic he had to take a mechanics course, when it came time for his
final the instructor told the class that they had to tear down and
reassemble a complete engine in order to score a perfect 100 on the test.  Our
friend the ex-gynecologist received his grade, 150.  Knowing the teacher said 100
was perfect he asked the teacher about his grade.  The instructor said,
"you got 50 points for tearing it down, 50 for rebuilding it, which gives you
the perfect 100.  I just had to give you an extra 50 though since you did
all of the work through the exhaust pipe."