The table that you will find at the end of the exercise corresponds to the duration of a sample of telephone calls (in minutes). A) Calculate the standard deviation of the sample of calls B) Determine the interval between 2 standard deviations. C) If the distribution is skewed, what percentage of the values are expected to fall within 2 standard deviations? Classes Frequency 2-4 2 5-7 6 8-10 7