I need help with compute the standard deviation o for age of super shoppers.

MIT INUTES MOR TUUR TEACHER What is the age distribution of promotion-sensitive shoppers? A supermarket super shopper is defined as a shopper for whom at least 70% of the items purchased were on sale or purchased with a coupon. Age range, years 18-28 29-39 40-50 51-61 62 and over Midpoint x 23 34 45 56 67 Percent of super shoppers 8% 43% 21% 9% 19% LA USE SALT For the 62-and-over group, use the midpoint 67 years