Which of the following statements are CORRECT? a. Cash fows fot an annuity due must occir at the end of the period b. The cash flows of an ordinary annuity oocur at the beginning of the petiod c.If a senes of unequal cash flows occurs at regular intervals, such as once a yoat, then the cash flow senies is by dofinition an annuity d. The cash fows tor an annuly may vary in amount from period to period, but they must oocur at regular intecvals, such as once a yoar or once a mo e. The cash flows for an annuity must all be equal, and they must occur at regular intervals, such as once a yeat of once a month