Please help me help this question. I can't find the answer.

There are two kinds of annunities. One is ordinary annuity, which means the same amount of payment occured at the end of each time period. The other is annunity due, which means the same amount of payment occured at the beginning of each time period. In the real world, what is the example of an ordinary annuity? What is the example of an annuity due? Which annunity is more common?

2. There are different ways to solve time value of money (TVM) problems. You can solve TVM problems by using (1) formulas or (2) Excel or (3) financial or graphing calculator's finance functions. Which one is best to use?