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. 2) $300 per month invested at 4%, compounded monthly, for 15 years; then $600 per month invested 2) at 7%, compounded monthly, for 15 years. A) About $418,557 B) About $759,769 C) About $400,507 D) About $264,005