AMO 2027 Grades 9-11 SET 4 - Self-study Question 8

In triangle $ABC$, $D$ lies on $AB$ with $BD=3AD$, and $E$ lies on $AC$ with $DE\parallel BC$. Point $F$ lies on the line $DE$ as shown, with $AB\parallel CF$. Find $EF$ if $BC=16$.



Choose one option.