Binomial model for counters drawn with replacement: exactly two greens, at least one green and the expected number of greens

A bag contains \(4\) green counters and \(20\) yellow counters. A counter is taken at random, its colour is recorded and it is then returned to the bag.

1. This is done \(10\) times. Find the probability that a green counter is taken[6]
   1. exactly twice;
   2. at least once.
2. The counter is taken and returned \(450\) times. Find the expected number of times that a green counter is taken.[2]