第二题:What if not all money need be invested? 可这样理解：
皆兄弟也
2010-09-08 10:37:04
( reads)
Investing 16 thousand dollars to 5 possible opportunities. To some of opportunities, 0 could be invested.
The fifth opportunity is investor's wallet. There is still some money in investor's wallet, not be invested yet.
So result is C(16+5-1,5-1) = C(20,4)