On average 20% of the gadgets produced by a factory are mildly defective. I buy a box of 100 gadgets. Assume this is a random sample from the production of the factory. Let A be the event that less than 15 gadgets in the random sample of 100 are mildly defective. (a) Give an exact expression for p(a), without attempting to evaluate it. (b) Use either the normal or the Poisson approximation, whichever is appropriate, to give an approximation of p(a).