Can you please explain how the expert got these answer? Thank you

3. For the grouped frequency distribution of daily high temperatures for City X: a. Calculate the mean and standard deviation b. Calculate the range of high temperatures within one, two and three standard deviations of the mean. Temeerature f % cf c% m fm fm2 20-29 9 2% 9 2% 25 225 5,625 30-39 23 6% 32 9% 35 805 28,175 40-49 32 9% 54 18% 45 1,440 64,800 50-59 75 21% 139 38% 55 4,125 226,875 50-59 90 25% 229 63% 55 5,850 380,250 70-79 77 21% 306 34% 75 5,775 433,125 80-89 34 9% 340 93% 85 2,890 245,650 90-99 19 5% 359 93% 95 1,805 171,475 100-109 6 2% 365 100% 105 530 66,150 Total 365 100% 23,545 1,522,125 Continued on the next page X-bar 64.51 52 283.0445 5 16.82393 Lower Upper Interval Bound Bound Xbar : 15 47.7 81.3 Xbar 2 25 30.9 98.2 Xbar : 35 14.0 115.0 Distribution of Daily High Temperatures 20-29 30-39 40-49 50-59 60-69 70-79 80-89 90-99 100-109 Temperature The question did not ask for a histogram of the temperature distribution [histogram rather than a bar graph because temperature is a continuous variable), but here it is. Note the symmetric shape. Because of that, the mode [60-69] and the median {65, if one interpolated within the 60-69 interval) are virtually identical to the mean {64.5}. In contrast, it is in skewed distributions that the mean diverges from the media and mode