Compute the present value of a $230 cash flow for the following combinations of discount rates and times. (Do not round intermediate calculations. Round your answers to 2 decimal places.) a. r= 10%; t= 9 years b. r= 10%; t = 18 years c. r= 5%; t= 9 years d. r= 5%; t = 18 years a. Present value b. Present value C. Present value d. Present value