Kenneth started saving for retirement at age 40 with plans to retire at age 70. He invested an average of $400 per month in various securities, with an average annual return of 7% adjusted for inflation. Assuming monthly compounding, how much has Kenneth saved at the start of retirement?


A. $487,988. 40
B. $720,421. 84
C. $37,784. 31
D. $556,559. 83


I got A but I wanted to make sure if I was correct, could someone help me?