During a Presidents' Day Sale, the 20 sales associates at Stephen's registered sales in the amounts shown below. Make a frequency distribution using $100 intervals (starting with $50), and determine ( a) the mean, (b) the median, and (c) the most typical sales interval (modal class). $155 $ 95 $ 75 $385 $190 420 160 50 260 330 170 50 180 175 240 140 250 300 80 200