Boston University AcademySTATISTICS 110  A researcher asked 25 customers: " how much would you pay for a television adapter with Internet Access?' Their grouped responses are as follows: Class Interval Frequency 0-99                       2 100-199                2 200-249                3 250-299                3 300-349                6 350-399                3 400-499                4 500-999                2   (a) calculate the mean of the dataset (b) calculate the variance of the dataset