math
posted by worried .
A young executive deposits $400 at the end of each month for 7 years and then increases the deposits. If the account earns 7.2%, compounded monthly, how much (to the nearest dollar) should each new deposit be in order to have a total of $400,000 after 25 years

Accumulated value after 7*12=84th payment
400((1+0.006)^841)/0.006=43522.55653
This amount after 25 years>158445
Let P new payments then
400000158445=P*((1+0.006)^2161)/0.006
241555=P*440.087
P=$549