12. (8 points) a) Suppose that a market research firm is hired to estimate the percent of adults who pay with a credit card at restaurants. Three thousand diners were randomly selected and 2,348 of them reported that they pay with a credit card. At the 90% level of confidence, find the margin of error, E, and the confidence interval estimate for the true population proportion of adults who pay with a credit card at restaurants. b) What sample size is required if the market research firm wishes that the estimate is within one percentage point with 95% confidence, assuming the firm uses the value of p obtained in part (b)? Read this carefully: Select three of the five problems from #13-17 that you want to be graded. Circle the three problems that you want to be graded, and the other two will be thrown out. If you do not indicate which problems you want graded, then the first three in a row will be graded regardless of whether any are left blank