please answer questions below

In the following situations, decide whether you would use a personal interview, observation, mailed questionnaire or telephone interview. Substantiate your answers. a) A poll of students at Open University on their preferences among five candidates who are running for president of the students' union. b) A survey of 50 hypermarkets, scattered throughout Mauritius, on their personnel management policies. c) A survey of financial officers of the Top 100 Companies to study their predictions for the economic outlook in their industries in 2021. Calculate the mean (u) and the standard deviation (0) of the normal variable X from the following data. P (x > 35) = 0.55; P (x