Exercise 3.

Find the following cardinalities:

  1. \(|A|\) when \(A = \{4,5,6,\ldots,37\}\text{.}\)

  2. \(|A|\) when \(A = \{x \in \Z \st -2 \le x \le 100\}\text{.}\)

  3. \(|A \cap B|\) when \(A = \{x \in \N \st x \le 20\}\) and \(B = \{x \in \N \st x \mbox{ is prime} \}\text{.}\)

in-context