Hi guys! I'm new in theory of probability and I'm having a hard time solving a probability problem. I'll be really grateful if you explain to me the solution.

So here's the problem:

Test for impurities commonly found in drinking water from private wells showed that 30% of all wells in a particular country have impurity A. If a random sample of five wells is selected from the large number of wells in the country, what is the probability that:

a) Exactly three will have impurity A?

b) At least three?

c) Fewer than three?