1. In order to study the length of time after billing for customers to settle the payments. a manager of a virtual bank took a random sample of 100 credit card invoices. A frequency table for the data on payment time, i.e., the number of days between the invoice date and the payment receipt date, was constructed as below. Payment time (in days) Number of invoices 0 - 9 7 10 - 19 20 20 - 29 48 30 - 39 19 40 - 59 6 (a) Calculate the mean, mode, standard deviation and interquartile range. 8 marks (b) Calculate the coefficient of skewness using results in (a) and interpret your result briefly. [2 marks]