The following data relates to the number of successful sales made by the salesmen employed by large microcomputer firm in a particular quarter. Number of Sales: 0-9 & 10-19 & 20-29 & 30-39 & 40-49 & 50-59 number of salesman: 1 & 14 & 23 & 21 & 15 & 6 Required; i) Calculate the mean number of sales. ii) Calculate the mode of sales. iii) Calculate Median of sales.