A researcher wishes to estimate, with 90% confidence, the population proportion of families who eat fast food at least once per week. Her estimate must be accurate within 4% of the population proportion. (a) No preliminary estimate is available. Find the minimum sample size needed. (b) Find the minimum sample size needed, using a prior study that found that 40% of the respondents said they eat fast food four to six times per week. (c) Compare the results from parts (a) and (b)