# CS 70 Reading Quiz -- Week 15, Sunday

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1. 130 CS70 students take the final exam. Suppose that all of these exams are shuffled thoroughly and then distributed to the class, one exam per student. Use Chebyshev's inequality to find an upper bound on the probability that at least five students receive their own exams.

(More formally, as discussed in the lecture notes: upper-bound the probability that a random permutation of 130 items has at least five fixed points. The lecture notes show that the expected value and variance of the number of fixed points is 1; you may use this freely, without proof.)

2. Is the set of prime numbers countable? Why or why not?

3. What did you find difficult or confusing about the reading or the lectures, and what would you most like to see explained better? If nothing was difficult or confusing, and you understand the material pretty well, tell us what you found most interesting. Please be as specific as possible.