Only one, but she/he'll have to go out and buy the light bulb adaptor card first, which is extra.
or
Two. One to take out the bulb and drop it, and the other to try and sell it before it crashes.
or
First they have to agree on which is better; the analog bulb or a digital bulb.
or
Two. One to take out the bulb and drop it, and the other to try and sell it before it crashes (knowing that it's already burned out).
or
Four. One to change the bulb and three to whine "It's too high"
or