Answer: Our required probability is 0.304.
Explanation:
Since we have given that
N = 21
Number of improperly drilled holes k = 4
Number of properly drilled holes = N-k= 21-4=17
Let X be the number of improperly drilled holes in a sample of 5.
We will use "Binomial distribution":

So, our required probability is 0.304.