Not making sense...probability

30% of calls to an airline reservation phone line result in a reservation being made.

a. Suppose that an operator handles 10 calls. What is the probability that none of the 10 calls results in a reservaion?

b. What assumption did you make in order to calculate the probability in part (a)

c. What is the probability that at least one call results in a reservation being made?

This probably won't be my last question. I'm not understanding statistics much and I've never been great shakes at maths. Thanks!