With $=\{2,3,5,7\},=\{2,4,5,8,9\}$ and $U=\{1$:$10\}$ compute. $(3$pts$)$

With $=\{2,3,5,7\},=\{2,4,5,8,9\},$ compute and. pts$)$

Use the proof by contradiction to show that if and only if $(10$pts$)$

How many substrings are in$,$ where $?(3$pts$)$