Binomial Distribution about ties

Question

A research team at Cornell University conducted a study showing that approximately 10% of all businessmen who wear ties wear them so tight that they actually reduce blood flow to the brain, diminishing cerebral functions. At a board meeting of 20 businessmen, all of whom wear ties, what is the probability that a)at least one tie is too tight b)no more that two ties are too tight c)no ties are too tight d)at least 18 ties are too tight