2/9 of H?... , um I think
The way you worded the question kind of confuses me but i'll try to answer.
Think of recursion like climbing a ladder; in this type of sequence you start out somewhere, usually n. So in f(n-1)+1, you take n (where you started) and "step down" once, and then step up once (which brings you back where you were). Remember PEMDAS when doing these.
Dont you have to have the beginning amount of water?
