Attention please!!!!!!!

a. In which situation, we use Permutation and Combination.

b. An MBA applies for a job in two firms X and Y. The probability of being selected in firm X is 0.7 and being rejected at Y is 0.5. The probability of at least one of his applications being rejected is 0.6. What is the probability that he will be selected by one of the firm?

c. Husband and wife appear in an interview for two vacancies in the same post. The probability of husband’s selection isand that of wife is. What is the probability that:

1. Both of them will selected

2. Only one of them is selected

3. None of them is selected.