A bias coin is tossed four times. If probability of head in a single toss is 0.61, find the probability of
i. at most 1 head.
ii. at least 2 heads.
b. Suppose X is a binomial random variable with n = 10 and p = 0.5,find
i. mean and variance of X.
ii. P(X = 5).
iii. P(X <= 4).