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Suppose that insurance companies did a survey. They randomly surveyed 400 drivers and found that 300 claimed they always buckle up. We are interested in the population proportion of drivers who claim they always buckle up. NOTE: If you are using a Student's t-distribution, you may assume that the underlying population is normally distributed. (In general, you must first prove that assumption, though.) Part (a) Part (b) Part (c) Part (d) Construct a 95% confidence interval for the population proportion who claim they always buckle up. (i) State the confidence interval. (Round your answers to four decimal places.) (ii) Sketch the graph. = C.L. = P' (iii) Calculate the error bound. (Round your answer to four decimal places.)