. Find the final amount (rounded to the nearest dollar in this retirement account, in which the rate of return on the account and the regular contribution change over time. $300 per month invested at 5%, compounded monthly, for 15 years; then $600 per month invested at 7%, compounded monthly, for 15 years, ad O A. About $726 606 OB. About $418,625 OC. About $270,364 OD. About $431,276 lee