Dilbert has a life annuity that he purchased for $95,000. His payment at the end of each month is $600.50 and the nominal interest rate is 4.7% compounded monthly. What is Dilbert's life expectancy according to the life insurance company's assumptions? O a) 20.47 years O b) 20.61 years W O c) 23.56 years O d) 27.33 years