A college professor hands out a list of 12 questions, 6 which will appear on the final examination for the course. One of the students taking the course is pressed for time and can prepare for only 7

A college professor hands out a list of 12 questions, 6 which will appear on the final examination for the course. One of the students taking the course is pressed for time and can prepare for only 7 of the 12 questions on the list. Suppose the professor chooses 6 questions at random from the 12. What is the probability that the student will be prepared for exactly 4 questions?