In a 1997 Marist Institute survey of 935 randomly selected Americans, 60% of the sample answered yes to the question, "Do you think there is intelligent life on other planets?" (a) What is the sample proportion of Americans who believe there is intelligent life on other planets? (b) What is the standard error of the sample proportion? (c) Calculate a 90% CI for the population proportion of Americans who believe there is intelligent life on other planets.