Engineer vs Doctor

[Porsche]

An Engineer was unemployed for a long time. He could not find a job so he opened a medical clinic and puts a sign up outside: “Get your treatment for $500, if not treated get back $1,000.”
One Doctor thinks this is a good opportunity to earn $1,000 and goes to his clinic. Doctor: “I have lost taste in my mouth.”

Engineer: “Nurse, please bring 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 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 medicine from box 22 and put 3 drops in the patient’s mouth.”

Doctor: “But that is Gasoline!” Engineer: “Congratulations! You’ve got your memory back. That will be $500.”

The Doctor leaves angrily and comes back after several more days. Doctor: “My eyesight has become weak.”

Engineer: “Well, I don’t have any medicine for this. Take this $1,000.”

Doctor: “But this is $500…”

Engineer: “Congratulations! You got your vision back! That will be $500.”