pleas show solution and answer for:Standard deviation and Variance

Given below is the distribution of 140 candidates marks X or higher in a certain examination (all marks are given in whole numbers): X: 10 20 30 40 50 60 70 80 90 100 C.f: 140 133 118 100 75 45 25 9 2 Calculate the mean, median and mode standard deviation and variance of the Distribution. Hint Class Frequency (f) Class Mid Value c.f. (less boundaries than) 10-19 140-133=7 9.5-19.5 14.5 V 20-29 133-118=15 19.5-29.5 24.5 22 30-39 118-100=18 29.5-39.5 34.5 40 40-49 100-75=25 39.5-49.5 44.5 65 50-59 75-45=30 49.5-59.5 54.5 95 60-69 45-25=20 59.5-69.5 64.5 115 70-79 25-9=16 69.5-79.5 74.5 131 80-89 9-7=7 79.5-89.5 84.5 138 90-99 2-0=2 89.5-99.5 94.5 140