Continuing to use the data in Exercise 1, consider once again only the nonzero observations. Suppose that the sampling mechanism is as follows: y* and another normally distributed random variable z has population correlation 0.7. The two variables, y* and z, are sampled jointly. When z is greater than zero, y is reported. When zis less than zero, both zand y are discarded. Exactly 35 draws were required to obtain the preceding sample. Estimate μ and σ.