6. From the 11 positive integers $1,2,3, \cdots, 11$, if 3 different positive integers $a, b, c$ are randomly selected, then the probability that their product $a b c$ is divisible by 4 is $\qquad$.
Let $A=\{1,3,5,7,9,11\}, B=\{2,6,10\}, C=\{4,8\}, M=$ “ $a b c$ is divisible by 4”, then $P(\bar{M})=\frac{C_{6}^{3}+C_{6}^{2} \cdot C_{3}^{1}}{C_{11}^{3}}=\frac{65}{165}=\frac{13}{33} \Rightarrow P(M)=\frac{20}{33}$.