Question

Which one is a function?

Set A contains zip codes from the US and set B contains US citizen's social security numbers. The elements of these sets can be paired in that each person has a zip code for their legal address (or domicile) and eachperson has a social security number. (a) If these are written as ordered pairs of the form (zip code; Social security number) do we have a function? Why or why not? (b) If these are written as ordered pairs of the form (Social security number; zip code) do we have a function? Why or why not?