find the amount of interest by the following deposit $3000 at 6.4% compounded semiannually for 2.8 years
Is interest paid at the end of each period? If so, then 2.8 years is the same as 2.5 years = 5 interest periods.
r = 6.4%/2 = 0.032
Final value = 3000*(1+r)^5 = 3000*1.032^5 = 3511.72
Interest = $511.72