Mark bought a cd for $500 that earns 3.9% apr and is compounded quarterly. the cd matures in 3 years. how much will this cd be worth at maturity?

First, we calculate for the effective interest rate.
                            ieff = (1 + 0.039/4)^4 - 1
                            ieff = 0.039574

then, the future worth of current amount is equal to,
                                      f = p x (1 + ieff)^n
where p is the current money and n is the number of years.
                                      f = ($500) x (1 + 0.039574)^5
                                                f = $607.08

The first one is 2/3the second is 1/160the third is 4/125