Refer to the previous exercise and now suppose that the chance experiment terminates only when two nondefective batteries have been obtained.

a. Let A denote the event that at most three batteries must be examined before the chance experiment terminates. What outcomes are contained in A?

b. Let B be the event that exactly four batteries must be examined before the chance experiment terminates. What outcomes are in B?

c. What can be said about the number of possible outcomes for this chance experiment?

Previous exercise

Suppose that, starting at a certain time, batteries coming off an assembly line are examined one by one to see whether they are defective (let D = defective and N = not defective). The chance experiment terminates as soon as a nondefective battery is obtained.