13. An 5R5 of 400 American adults is asked, "What do you think is the most serious problem facing our (4 points) schools?" Suppose that in fact 30% of all adults would answer drugs if asked this question. The proportion phat of the sample who answer drugs will vary in repeated sampling. In fact, you can assign probabilities to values of phat using the normal density curve with mean 0.3 and standard deviation 0.023. Use this density curve to find the probabilities of the following events: a) At least halfofthe sample believes that drugs are the schoolsr most serious problem. b} Less than 25% of the sample believes that drugs are the most serious problem. c] The sample proportion is between 0.25 and 0.35. 17. Write a story problem for which the following calculator command would be used in finding the solution. (4 points) a) Binomialpdf(20, 0.25, 12) b) Binomialcdf(20, 0.25, 12)