A chromosome mutation linked with colorblindness is known to occur, on the average, once in every ten thousand births.

(a) Approximate the probability that exactly three of the next twenty thousand babies born will have the mutation.

(b) How many babies out of the next twenty thousand would have to be born with the mutation to convince you that the "one in ten thousand" estimate is too low? [Calculate P(X ≥ k) = 1 − P(X ≤ k − 1) for various k.