Money invested = $1420
Final money = $1621.4
Effective yield = [ 1 + i/n]^n - 1
i = nominal rate let's consider 10%
n = number of payments 12 payments because it is in a year
Effective yield = [1 + 0.1/12]^12 - 1
= [ 1 + 0.00833]^12 - 1
= [1.0083]^12 - 1
= 1.1 - 1
Effective yield = 0.10 %