Engineer

[Rondy]

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 £1,000 if we fail."
A Doctor thinks this is a good opportunity to earn £1,000 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 petrol!"
Engineer: "Congratulations! You've got your taste back. That will be £500."
The Doctor gets annoyed and goes back after a couple of days later to recover his money.
Doctor: "I have lost my memory, I cannot remember anything."
Engineer: "Nurse, please bring the medicine from box 22 and put 3 drops in the patient's mouth."
Doctor: "But that is petrol!"
Engineer: "Congratulations! You've got your 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 £1,000," passing the doctor a £500 cheque.
Doctor: "But this is for £500..."
Engineer: "Congratulations! You've got your vision back! That will be £500."