i have a question, if possible, I need some one to help me to solve it. I know it's easy but it kind make me dizzy.

if a cable is manufactured with probability of 0.001 that has one blemish per foot and probability of 0 for more than a blemish with same length. If X is the number of blemish per 3000 feet, get the Pr(X=5) ??

is the solution will be as follow:

mu = n * p = 3000 * .001 = 3

Pr(X=5) = [ 3^5 * e^(-3) ] / 5! = .100 =10% (Poisson Distribution)