For the marketing personnel, we have a binomial distribution with n = 15 and p = 0.75. Then the probability of k extroverts is (15 choose k) * 0.75^k * 0.25^15-k

(a) p(10 or more) = p(10) + p(11) + ... + p(15) = 0.85163192265

p(5 or more) = 1 - p(4 or less) = 1 - (p(0) + p(1) + p(2) + p(3) + p(4)) = 0.99988466408

p(15) = 0.01336346101

For the programmers, n = 5 and p = 0.65. Then the probability of k introverts is (5 choose k) * 0.65^k * 0.35^5-k

(b) p(0) = 0.0052521875

p(3 or more) = p(3) + p(4) + p(5) = 0.764830625

p(5) = 0.1160290625

QUESTION: how do I find out what p(3) or p(4) etc. is?