Seven. One to install the new bulb and six to figure out what to do with the old one for the next 10,000 years.
or
To get his filling!
or
Between you and me, something smells.
or
None. Bill Gates will just redefine Darkness® as the industry standard.
or
"Let me see your birth certificate".
or
Four. One to change the bulb and three to whine "It's too high"
or