Chess Knight Move

One day, in line at the company cafeteria, Joe says to Mike behind him, 'My elbow hurts like heck. I guess I'd better see a doctor.'
'Listen, you don't have to spend that kind of money,' Mike replies.
There's a diagnostic computer down at Costco. Just give it a urine sample, and the computer will tell you what's wrong and what to do about it.
It takes ten seconds and costs ten dollars - a lot cheaper than a doctor.
So, Joe deposits a urine sample in a small jar and takes it to Costco.
He deposits ten dollars and the computer lights up and asks for the urine sample. He pours the sample into the slot and waits.
Ten seconds later, the computer ejects a printout:'You have tennis elbow.
Soak your arm in warm water and avoid heavy activity. It will improve in two weeks.
Thank you for shopping @ Costco'

That evening, while thinking how amazing this new technology was, Joe began wondering if the computer could be fooled.
He mixed some tap water, a stool sample from his dog, urine samples from his wife and daughter, and a sperm sample from himself for good measure.
Joe hurries back to Costco, eager to check the results.
He deposits ten dollars, pours in his concoction, and awaits the results.
The computer prints the following:
1. Your tap water is too hard. Get a water softener. (Aisle 9)
2. Your dog has ringworm. Bathe him with anti-fungal shampoo. (Aisle 7)
3. Your daughter has a cocaine habit. Get her into rehab.
4. Your wife is pregnant -- Twins. They aren't yours. Get a lawyer.
5. If you don't stop playing with yourself, your elbow will never get better!
Thank you for shopping @ Costco!