Just one, but it takes a really long time, and the lightbulb has to want to change...
A what?
None- that's hardware.
Three. One to do it, one to complain that it has already been done before, and one to repost this joke.
Find out next time on Dragon Ball Z***
One, but only if the lightbulb really to change.
He was bipolar.
Long time no see.