LOL you needed pencil and paper to understand me?
Cool. Anyway, yeah i did forget to add in the 12MW of electricty per year. Okay the formula for that is,
12/Overall power produced divided by No. of engineers = Answer A.
Next take the engineers pay and divide it by answer A and you should get answer B. Take answer B and add it to the saved up amount of cash for not having extra 2 workers in the cigar factory per month AND it will also be added to the fact that you still need 33 years to pay of the cost of the auto rollers before you are actually saving cash in that case with electricity cost, you need even longer now. perhapes even the whole of 50 years or so (Just a guess)
My conclusion. NO AUTO ROLLERS! You save $30k compared to the amount you can save from 2 factory worker's wages - the electricity cost.... NO AUTO ROLLERS! NO AUTO ROLLERS! SAVE THE ELECTRICITY!