Technically, choice-A is the process involved. But it's already been done, and widely published, and the spectrum of every element is easily available.
For you to take the time and go to the trouble of constructing the spectra would be like inventing wheels if you want to ride a bicycle.
The used work of energy output is 496*2.1=1041.6 J. And the actual work of energy output is 1127*0.85=957.95 J. The percentage efficiency is 957.95/1041.6*100%=91.97 %.
