encounter a sequence of birds while walking in the park. The birds can either be blue (B) or red (R). We let X be the random variable corresponding to the number of birds we encounter until seeing the first blue one. (That is, if we see the pattern RRRB, X = 4.) Suppose each bird is red with probability = 3/4 and blue with probability = 1/4 (The color of one bird doesn't affect the color of any other bird.)
(a) Determine the probability mass function (PMF) of X.
(b) What type of random variable is X?
(c) Use the PMF to find the smallest integer value of N such that P(X > N) < 0.001.