Suppose that 10% of all bits transmitted through a digital communication channel are erroneously received and that whether any particular bit is erroneously received is independent of whether any other bit is erroneously received. consider sending a very large number of messages, each consisting of 20 bits.

(a) what proportion of these messages will have a t most 2 erroneously received bits?
(b) what proportion of these messages will have at least 5 erroneously received bits?
(c) what is the expected number of erroneously received bits per message?