moderator – please replace my earlier “cleaned up” version with this one. the data i put in the earlier post inadvertantly contained HTML tags, which is messing up the page and making my posting unreadable. sorry!
2) The only numbers that give six or more bills in change from $40 are $1, $2, $6, $11 and $21. If margarita $ = x and lemonade $ = y and x / 2 >= y (cond. 5), x can only be $6 or $11, y can only be $1 or $2. Since x * 1.5 + y must be $11 or $21, the only combo that works is x(margarita) = $6, y(lemonade) = $2
3) Water * 3 <= lemonade. Since only vodka has a non-integer price, water = $0.
4) The coin in change can only be a quarter (the whole dollar amounts of drinks can only be divided by 2, and vodka * 4 = an integer).
5) The total is over $20 ($11 margarita and lemonade, at least $4 for the rum, at least $4.25 for the vodka an at least $1 for the Pepsi). This means the change can either be $2.25, $6.25, $11.25 or $15.25 (two bills, one quarter).
7) Rum is $4.50 or $6 (floor = 2 * lemonade, ceiling = margarita). A second rum returns >= (six coins + bills) change. This only works if the second rum is $2.50. Rum = $5.