关于effective annual rate的美国数学题

题目

关于effective annual rate的美国数学题
Steven purchased 1000 shares of a certain stock for $30,000 (including commissions).He sold the shares 2 yr later and received $34,400 after deducting commissions.Find the effective annual rate of return on his investment over the 2-yr period.(Round your answer to two decimal places.)

答案

presume effective annual rate=x
30(1+x)²＝34.4,
x=0.07(two decimal places.)