Fund X is valued at a nominal annual interest rate of 0.12, which can be converted into three months. Y fund is valued at a nominal annual interest rate of 0.08, which can be converted to six months. At the beginning of the first year, certain amounts were invested in both funds. At the end of the 6th year, both funds the total amount was $ 20,000. At the end of the 4th year, the cumulative value of fund X is equal to twice the cumulative value of fund Y. Find the amount invested in fund X since it is.