Which one of the following is an ordinary annuity? 1) $25 paid every year for ten years, starting today O 2) $50 paid weekly for 1 year, starting one week from today 3) $75 paid at the beginning of each monthly period for 50 years O 4) $40 paid quarterly for 5 years, starting today O 5) $15 paid at the end of each monthly period for an infinite period of time