looking for effective rate of return!!

Sandra Robinson is planning to buy 10 -year zero coupon bonds issued by the U.S. Treasury. If these bonds have a face value of $1,000 and are currently selling at $405.29, what is the expected return on them? Assume that interest compounds semiannually on similar coupon paying bonds, (Round intermediate colculations to 5 decimal places, es. 1.25145 and final answer to 2 decimal places, es. 15.25%.) Effective rate of return