how do you get that answer?

2-13 A bank (through its TV ads) is trying to interest you in an IRA (individual retirement account). They say that if you invest $2,000 per year for the next 40 years in their IRA, you will have a nest egg of $600,000 to retire on. a) What interest rate are they using assuming the money is deposited at the end of the year and that the compounding period is yearly? Ans: "i" is approximately equal to 8.6%