you are interested in the effect of personal computer ownership on high-school GPA: GPA, a+8 PC, +E where . GPA, high-school GPA of kid i PC: 1 if kid owns personal computer (a) Explain why might the effect of PC be confounded with parents' annual salary. (b) Suppose that a year ago the government gave grants to buy personal computers to randomly chosen high- school kids. Explain how you would construct an instrument for estimating the effect of PC ownership. (c) Explain in English the LATE that you are estimating with your instrument in (b). (Hint: first check if there will only be compliers or defiers, and then define LATE.) (d) Suppose instead that the government gave grants to buy personal computers to high-school kids from low- income family. Explain how this makes the instrument that you constructed in (b) an invalid instrument.