An annuity stream of cash flows is: Select one: a. A set of level/equal cash flows occuring each time period for a fixed length of time. b. A set of level/equal cash flows occuring each time period forever. c. A set of increasing cash flows occuring each time period for a fixed length of time. d. A set of increasing cash flows occuring each time period forever. e. A set of arbitrary cash flows occuring each time period for no more than 10 years. f. A single cash flow that is uncertain