The correct answer is A but I am not sure how to get it. thanks.

Betty has just retired. She plans to use her life savings of \$Ato buy an annuity. She has narrowed her choices to the following three banks: Bank A: j12=x%, with monthly payments of RA for 20 years, first payment due in one month Bank B: j12=x%, with monthly payments of RB for 18 years, first payment due in one month Bank C:j12=x%, with monthly payments of RC for 20 years, first payment due today Which of the following is true? 'A. RARC B. RA>RB and RA>RC C. RA>RB and RA