please answer thoroughly

(8 points) You are comparing different saving schemes and want to find out which one will get you most money if you invest the annual equivalent of $18,000 for the next 15 years when annual interest over those 15 years is 7.50%. How much will you end up with if you save that $18,000 : a. Once per year (annually) b. Twice per year (semiannually) c. Four times per year (quarterly) d. Twelve time per year (monthly)