Each USB stick produced by certain factory has 0.065 probability of being defective, regardless of other USB sticks produced. The factory sells them in packages containing 30 and guarantees a refund if a costumer buys a package and at least one pendrive is defective.
a) What is the probability of the factory having to refund a client?
b) If a customer buys 9 packages, what is the probability that he/she receives his/her money back for just one of them?
I have the answers here, I just can't figure out how to achive them
a)0.867
b)0 (zero)