3. a. The age of some students are: 3, 13, 7, 5, 21, 23, 33, 40, 23, 14, 12, 56, 32, 45, 9, 13, 32, 26, 24 and 35. Calculate their mean, median age and modal age. Mention which measures of central tendency is appropriate to use here with proper explanation.

b. Explain with an example when arithmetic mean should not be used as a measure of central tendency.