Forty-six cities provided information on vacancy rates (in percent) for local apartments in the following frequency distribution Vacancy Rate (in percent) Frequency 0 up to 3 13 3 up to 6 6 up to 9 9 up to 12 12 up to 15 10 11 a. Calculate the average vacancy rate. (Round your answer to 2 decimal places.) Average vacancy rate b. Calculate the variance and the standard deviation for this sample. (Round intermediate calculations to at least 4 decimal plac and final answers to 2 decimal places.) Variance Standard deviation