A fraction p of items from a certain production line is defective.

a) What is the probability that there is more than one defective item in a batch of n items?

b) There is a probability of q = 0.1 that the production line malfunctions. During normal production p = 0.01 but when production malfunctions p = 0.4. Find the size of a batch that should be tested so that if any items are found defective we are 70% sure that there is a production malfunction.