Hey, I'm a little stuck on this problem!

That's the only one left on my pset, which is due today 10:am pacific Time. Was wondering whether you could help me to get unstuck! I appreciate

Say that of all the students who will attend university X, each will buy at most one laptop computer when they first arrive at school. 40% of students will purchase a PC, 30% will purchase a Mac, 10% will purchase a Linux machine and the remaining 20% will not buy any laptop at all. If 15 students are asked which, if any, laptop they purchased, what is the probability that exactly 6 students will have purchased a PC, 4 will have purchased a Mac, 2 will have purchased a Linux machine, and the remaining 3 students will have not purchased any laptop?