Your second function doesn't have to be terribly exotic. If you pick a power of a sine function added to a polynomial then you will have infinitely many extrema because the power of the sine function will oscillate along the polynomial. You could use a function like this but you would then want to limit your attention to the extrema near the origin. Why don't you look at an algebraic function that will have some fractional powers along with some integer powers. If your fractional powers have only positive odd roots then your functiuon will be defined on the entire real line.
My intention with you choosing an interesting function for part b is for you to use the tools of calculus with a powerful piece of saftware to gain insight into the appearance and behaviour that you wouldn't have been able to get otherwise.
Even something like the example, (that I never had a chance to investigate last class), y = 10x / ( x2 + 1) would be fine.
--CFW