In a certain store, there is a .03 probability that the scanned price in the bar code

Question:

In a certain store, there is a .03 probability that the scanned price in the bar code scanner will not match the advertised price. The cashier scans 800 items.
(a) What is the expected number of mismatches? The standard deviation?
(b) What is the probability of at least 20 mismatches?
(c) What is the probability of more than 30 mismatches? Show your calculations clearly.