Solution

ID: past-exam-of-the-logic-and-set-theory-course-of-the-university-of-oxford/2007/b/7/ii/solution

The set of all functions from a set of size to another set of size has size . Cardinal exponentiation and the law give
Therefore
The lower bound can also be seen by taking characteristic functions of all subsets of . Cantor's theorem makes this strictly larger than , unlike the continuous-function space in the next part.

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