Test and analysis: (1) Mark the eligible events first, and then calculate the probability of passing the rematch according to the conditions given in the test. (2) Answer directly according to the probability calculation method of discrete random variables.

Test analysis: (1) Note that A passing four courses is an event, so the probability that "A can get credit for this course" means that the event is independent.

.

(2) , , ,

Because ~

therefore