The age (in months) at which a child begins using a certain type of sentence structure is recorded for 60 children. The frequencies of four categories are given in the table below.

Age (months) midpoint frequency 24 - 29 26.5 15 30 - 35 32.5 8 36 - 41 38.5 13 42 - 47 44.5 24

1. If one of these 60 children is selected at random, find the probability that the age of that child is:

a) at most 41 months

b) no less than 36 months

c) between 30 and 41 months (inclusive)