According to survey conducted by TD Ameritrade, one out of four investors have exchange-traded funds in their portofolios(USA Today, January 11, 2007). Consider a sample of 20 investors. A. Compute the probability that exactly 4 investors have exchange-traded funds in their portfolios. B. Compute the probability that at least 2 of the investors have exchange-traded funds in their portfolios. C. If you found that exactly 12 of the investors have exchange-traded funds in their portfolios, would you doubt the accuracy of the survey results? D. Compute the expected number of investors who have exchange-traded funds in their portfolios.