A box contains a shipment of N N 4 computer chips of which

A box contains a shipment of N (N > 4) computer chips, of which four are defective. Four chips are randomly selected and examined as to whether or not the chips are defective. Describe the sample space for this experiment. What is the probability that:

How many different combinations are in the sample space?

(a)    Exactly one of the four chips is defective?

(b)    All four chips are defective?

(c)    Two chips are defective?