(c) A marketing researcher wants to estimate the mean amount of money spent on an eCommerce platform by its members. Suppose a random sample of 100 members who recently made a purchase on that platform has a mean of RM1,100 and a standard deviation of RM150. (i) Determine a 90% confidence interval estimate for the mean spending for all the members of that platform. (4 marks) (ii) Interpret the interval constructed in (i). (2 marks) (d) An advertising company wants to estimate the mean weekly amount of time consumers spend watching YouTube per day. Based on previous studies, the standard deviation is 20 minutes. (i) Suppose the company wants to estimate, with 95% confidence, the mean weekly amount of time to within 16 minutes. How many consumers need to be selected randomly? (3 marks) (ii) Is a sample size of 65 sufficient to estimate the mean weekly amount of time to within 14 minutes with 90% confidence? Justify your answer. (3 marks) [Total: 25 Marks]