Question: 1. Give an example of a graph that has a Hamilton circuit but not an Euler circuit. Explain.
2. Show that for 
3. What percentage of (theoretical seven-digit) phone numbers have all digits distinct?
4. Give three examples of functions f : Z → Z, where one is one-to-one but not onto, the second is onto but not one-to-one, and the third is neither oneto-one nor onto.