An urn contains 3 white and 6 red balls. Four balls are drawn one by one with replacement from the urn. Find the probability distribution of the number of red balls drawn. Also, find the mean and variance of the distribution.

Let p = probability of drawing a red ball

Let number of red balls drawn be X.

X follows a binomial distribution with,

The required binomial distribution is given by,

So, mean = np

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