Answer:
12.683%
Explanation:
The effective annual rate is given by ...
(1 +r/n)^n -1
where r is the nominal annual rate, and n is the number of compoundings per year. Filling in the given numbers, we have ...
effective rate = (1 +0.12/12)^12 -1 ≈ 0.12683 = 12.683%