$200 is the original price, not counting the amount of guests, therefore 200 is the b value
15 is dependent on the amount of quests, so you must multiply 15 to the amount of guests. But, since the number of guests remains unknown, you put in a variable for that.
I think it would be A, because if she jogged the same amount each day she jogged then all you need to do is multiply how much she jogged by how many days she jogged.
