A company’s machine breaks down. The company’s owner, an old school chum of Niels Bohr, calls in the physicist for help in fixing it.

Bohr examines the machine. He draws an X on the side and says, "Hit it right here with a hammer."

The company’s mechanic hits the machine with a hammer. It springs into action. The company’s owner thanks Niels Bohr profusely and sends him on his way.

A few days later, the owner receives an invoice from Bohr for $10,000. Shocked, the owner phones Bohr!

"Niels! What’s this $10,000 invoice? You were only here for 10 minutes! Send me a detailed invoice."

Bohr agrees to send the invoice. A few days later, the company’s owner opens a new invoice.

INVOICE

Drawing X on the side

of your machine $ 1

Knowing where to

put the X $ 9,999

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Total $10,000