There exist two different solutions.
It is not the case that A, where A is the formula from point (1).
Explanation concerning "exactly two". Suppose a man comes to a friend and asks to borrow $100 for a week until the end of the month. The friend asks him how much money he has now, and he answers that he has $10. So the friend lends him a hundred bucks. However, if the friend knew that the man has $2000 available in a checking account besides $10 in cash and wants $100 for a night in a casino, their friendship would probably be in danger.