Answer:
Effective annual rate is 6.25%
Explanation:
Effective annual interest rate is real interest rate. Nominal rate does not reflect compounding interest or fees on some financial products like loans. Effective does and is calculated as following:
( 1+ i/n)^n - 1, where i is nominal interest rate and n is the number of periods. If 321 dollars is the sum of monthly payments calculated as 15.408 * x * 48/12= 321, which gives its effective monthly rate of 0.5% or annual rate of 6.25%.