An engineer who was unemployed for a long time decided to open a clinic. He puts a sign outside his clinic: "A cure for you ailment guaranteed at $500; We'll pay you $1000 if we fail."
A doctor thinks that this is a good opportunity to earn $1000, and goes to his clinic.
Doctor: I have lost my sense of taste.
Engineer: Nurse, please bring the medicine from box 22 and put 3 drops in the patient's mouth.
Doctor: This is gasoline!
Engineer: Congratulations! You have you taste back. That will be $500.
The doctor gets annoyed and goes back a couple of days to recover his money.
Doctor: I have lost my memory. I can't remember anything.
Engineer: Nurse, please bring the medicine from box 22 and put 3 drops in the patient's mouth.
Doctor: But that is gasoline!
Engineer: Congratulations! You have you memory back. That will be $500.
The doctor leaves angrily and comes back after several days, more determined than ever to make his money back.
Doctor: My eyesight has become weak.
Engineer: Well I don't have any medicine for this. Take this $1000 *passing the doctor a $500 note*
Doctor: But this is $500...
Engineer: Congratulations! You've got your vision back! That will be $500.
