that was very close. I tis actually quite easy! you get the 2.5 by I/2ing the K-1+4/5, which is 0.5, then times it by optimus prime to get 5, and then times that by a further 100 to get 500, then realise you don't have a clue and guess!
I also get 6/5, or 1.2. There is a possibility that there is a misprint, that we are both wrong, or that you have miscopied the problem. All three of those things are likely.