I am thinking about this question and I don’t really know how to tackle it.

The problem is:

The class has 30 students. If you want to call 5 students, each one is independent of the others and randomly with equal probability, what is the probability that none are repeated?

I am thinking as 30* 29 * 28 * 27*26 / 30^5, but I am not sure it is correct. Thank you so much!