33. We have 20 thousand dollars that must be invested among 4 possible opportu-

nities. Each investment must be integral in units of 1 thousand dollars, and there are minimal investments that need to be made if one is to invest in these opportunities. The minimal investments are 2, 2, 3, and 4 thousand dollars. How many different investment strategies are available if

(a) an investment must be made in each opportunity;

(b) investments must be made in at least 3 of the 4 opportunities?

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