You plan to save $$390$ per month starting today for the next $48$ years "just to start the month off right."

$x$ You feel that you can earn an interest rate of $9\mathrm{.}5$ percent compounded monthly. How much will there be

in the account $48$ years from today?

I am still getting the answer as $$4,575,688\mathrm{.}51$ but the correct answer is $4,611,912\mathrm{.}71.$ can you explain how they derive to that answer?