The "compound amount" formula is A = P(1+r/n)^(nt),
where P=original investment, r=interest rate as a decimal fraction; n=number of compounding periods, and t=number of years.
Then A = $12000 * (1+0.08/2)^(2*11)
= $12000(1.04)^(22) = $28,439.03 (answer)