thank you all for the quick responses.
i hope it will be easy.
this entire ordeal has been so frustrating.
the note book, from a long distance school, often has mistakes. and when one is in the stages of learning for the first time, or even worse, reviewing after way too long at altitude, it is difficult to discern a mistake on their part- from a misunderstanding on my part- from an oversight on my part-from an assumption on their part-from an ....blah blah blah. then even the CAP doesn't explain each step along the way.
last night after making the post, i checked the oxford's again and i couldn't find the reason they included it.
for some one at my stage, especially in given examples, each little step should be explained clearly at the moment the factor is used in the calculations. at least once!
and it is so frustrating when i come across something like that on a late friday afternoon, especially in the holiday season.
thanks again