4. A store manager wishes to be 90% confident that his estimate for the mean monthly family grocery expense is correct within 1500 pesos. Based on the prior information, he believes that the monthly family grocery expense follows a normal distribution, and has arrived at an estimate of Php9000 for the standard deviation. Determine the minimum number of families to be taken as sample to meet his criteria.3. In the pulse Asia study, 31% of the 1200 adults polled said that fighting criminality is one of the top three urgent national issues. How large a sample if a similar study is to be conducted and wishes to be 90% confident that the estimated percentage will be within 2% of the true percentage?Problem Solving: 1. The owner of a gasoline station wishes to determine the proportion of its customers who pay using credit card or debit card. He decides to check the payment records of 200 customers and finds that 120 of them paid in cash. Construct a 95% confidence interval for the true proportion of customers who pay by credit or debit card. 2. In a random sample survey, 250 young professionals who work in Makati are asked whether they commuted to the city or brought their own car. If 88 of them commuted to work, construct a 99% confidence interval for the true proportion who commute to work