A mainframe computer on which everyone in the office depended
 suddenly went down.
 
 They tried everything but it still wouldn't work. Finally they
 decided to call in a high-powered computer consultant.
 
 He arrived, looked at the computer, took out a small hammer and
 tapped it on the side. Instantly the computer leapt back to life. 
 Two days later the office manager received a bill from the
 consultant for $1,000.
 
 Immediately he called the consultant and exclaimed, "One thousand
 dollars for fixing that computer?! You were only here five
 minutes! I want the bill itemized!"
 
 The next day the new bill arrived. It read,
 
 Tapping computer with hammer:  $1
 Knowing where to tap:  $999