Memory chips are defective with probability p 0001 independ

Memory chips are defective with probability p = .0001, independently of one another. Show the probability of a batch of n chips containing at most one defective is approximately e^-np(1 + np). Explain what kind of random variables you are using, and why. A batch of 10000 chips contains more than one defective. Find the approximate probability it contains exactly two defectives. The manufacturer requires that at least 98% of batches contain at most one defective. What is the largest allowable batch size?

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