Suppose that 50% of the watches produced by a certain factory aredefective. A store buys a box with 400 watches produced by this factory. Assumethat this is a random sample.(a) Write an expression for the exact probability that at least 215 watches out ofthe 400 are defective. You do not need to numerically evaluate it.(b) Argue whether the normal or the Poisson approximation is appropriate to es-timate the above probability and then estimate