4. Distribute 8 model student quotas to 4 classes, Jia, Yi, Bing, and Ding, with each class getting at least 1 quota. The probability that Class Jia gets exactly 2 quotas is $\qquad$ .
Distribute 8 quotas to four classes, A, B, C, and D, with each class getting at least 1 quota. The number of ways to do this is $C_{7}^{3}=35$. Distribute 6 quotas to three classes, B, C, and D, with each class getting at least 1 quota. The number of ways to do this is $C_{5}^{2}=10$. Therefore, the probability that class A gets exactly 2 quotas is $P=\frac{10}{35}=\frac{2}{7}$.