4. An analyst would like to study the percentage of revenue spent on product development by the companies of industry A in 2013. A random sample of companies is selected and the results are shown below: (a) Calculate the mean, median, standard deviation and coefficient of variation. (b) Estimate, from the frequency distribution table, the proportion of companies of industry A that spent between 8.2% and 11.6% of revenue on product development in 2013. (c) Estimate, from the frequency distribution table, the range of percentage of revenue spent on product development in 2013 for the middle 80% of companies..