(b) The continuous data are grouped in three classes as 0-4., 4-12 and 12-20. The fmqueocy densities of the classes 0-4 and 12-20 are in the ratio 5:2 and the total frequency of these two classes is 144. Calculate the least possible frequency of the modal class, given that the modal class is 4-10. {6 marks} (Total: 20 marks)