The Engineer was unemployed for a very long time. He could not find a job so he opened a medical clinic and put outside a sign saying "Get your treatment for $500, if not cured get back $1,000.
The Doctor thought that this was a good opportunity to earn $1,000 and went to the clinic.
Doctor I have lost the taste in my mouth.
Engineer Nurse Please medicine from Box 22 and put three drops in the patient's mouth.
Doctor. This is gasoline.
Engineer. Congratulations, you have your taste back. That will be $500.
Doctor gets annoyed and goes back after a couple of days to recover his money.
Doctor. I have lost my memory I cannot remember anything.
Engineer. Nurse please bring medicine from Box 22 and put 3 drops into the patient's mouth.
Doctor. But that is gasoline.
Congratulations, you have your memory back. That will be $500.
Doctor leaves angrily and comes back several days later.
Doctor. My eyesight has become weak.
Engineer. Well, I do not have medicine for that. Here is $1,000.
Doctor. But this is only $500.
Engineer. Congratulations. You have your vision back. That will be $500.