The table gives the ages of a sample of householders in primary families. Use this table in Problem.

Age of Householder (years)                 Number (thousands)

15–24 ............................................................... 3395

25–34 ............................................................... 13,347

35–44 ............................................................... 17,547

45–54 ............................................................... 18,119

55–64 ............................................................... 13,462

65+     ............................................................... 12,978

Use class marks and the given number (frequency) in each class to find the mean and standard deviation of the ages of the householders. Use 74 as the class mark for the 651 class.