A company produces and ships 16 personal computers knowing that 4 of them have defective wiring. The company that purchased the computers is going to thoroughly test three of the computers. The purchasing company can detect the defective wiring. What is the probability that the purchasing company will find the following?
a. No defective computers?
b. exactly three defective computers?
c. two or more defective computers?
d. one or fewer defective computers?