The light bulb doesn't do any "work" ... it doesn't exert force,
or maintain a force through a distance. It does, however,
dissipate energy, in the form of heat and light.
The quantity of energy that it dissipates is ...
(4 watts) x (8 hours) x (3600 sec/hour) x (1 joule/watt-sec)
= (4 x 8 x 3600) joules = 115,200 joules .
