Since you want a quantitative result, that is, your answer has a number in it, you'll want the one of your two options that is a formula, and not the one that is just a definition/theory/description. Can you tell them apart, and let us know, which is which?

I'm not trying to confuse you by being obscure, but this is how we help on this forum, we give hints, that help you learn, so you're better off for your next question.