"Suppose that f : A to B is a map. We define the graph of f to be Graph(f) = {(a, f(a) | a element of A} so Graph(f) subset of AxB."

Now the part of the question I'm interested in:

"Suppose that A and B are both finite sets, and that |A| = a and |B| = b. How many subsets G of AxB are graphs of functions from A to B?"

I got 2^(a+b). Is this correct? I find the question hard to understand but I think it's asking how many possible subsets are there of AxB? In which case I did that P(|A|) = 2^a and P(|B|) = 2^b therefore the total number of combinations is 2^a * 2^b = 2^(a+b). Correct? Probably not?

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