The weekly pocket money (in ₹) of students of a class is recorded below.
Class interval: 40–50, 50–60, 60–70, 70–80, 80–90, 90–100
Frequency: 14, 17, a, b, 12, 10
It is known that:
(i) The mode of the distribution is ₹66.
(ii) The frequency of the class 70–80 is 6 less than that of the modal class.
Determine the missing frequencies a and b.