Jo likes to drink beer up to a point. Her satisfaction from drinking glasses of beer in one evening is given by the function f(x) = x(8 - x). A glass of beer costs $5, and Jo has $15 dollars in her pocket and no credit or debit card.

1.If she wishes to maximize her satisfaction from drinking beer and somebody offers to buy beer for her, how many glasses will she drink?

2.If she must pay for the beer herself, how many glasses will she drink?