請教解數學題。

來源: 於 2010-09-06 18:14:36 [博客] [舊帖] [給我悄悄話] 本文已被閱讀：次

We have 20 thousand dollars that must be invested among 4 possible opportunities. Each investment must be integral in units of 1 thousand dollars.
How many different investment strategies are possible?
What if not all money need be invested?