One day, at the clinic...

An engineer who was unemployed for a long time decided to open a medical clinic. He puts a sign outside the clinic: "A cure for your ailment guaranteed at $500; we'll pay you $1000 if we fail."

A local doctor thinks this is a good opportunity to earn a thousand bucks, so he goes to the clinic.

Doctor: "I've 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've got your taste back. That will be $500."

The doc gets annoyed and goes back after a couple of days to recover his money.

Doctor: "I've 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's gasoline!"

Engineer: "Congratulations! You've got your memory back. That will be $500."

The doctor leaves angrily, and after several days, returns - determined more than ever to get his money back.

Doctor: "My eyesight has become weak."

Engineer: "Well, actually, I don't have any medicine for that.  Here, take this $1000"

Doctor: "This is gasoline!"

Engineer: "Congratulations! You've got your taste back. That will be $500," passing the doctor a $500 bill.

Doctor: "But this is only $500!"

Engineer: "Congratulations! You've got your eyesight back. That will be $500."