Alight bulb does 100 joules of work in 2.5 seconds. how much power does it have.

Well, light bulbs don't exert a force which then acts through a distance,
so they don't actually do any work.  But they do distribute energy, in
the form of visible and infrared radiation.

Power is the rate of transferring energy.

         (100 joules) / (2.5 seconds)  =  40 joules/second

                                                       =  40 watts  

Efficiency is an action of doing something. for example when you take a test. good efficiency means you did well but bad effeciency or no effiency means you did bad.