The ages of 25 students of a class are given below: 11, 11,11, 11, 11, 11, 11, 12, 12, 12, 12, 12, 12, 12, 12, 12, 13, 13, 13, 13, 13, 14, 14, 14, 15.construct a discrete frequency table and find the standard deviation.​