A customer service division of a telecommunications firm

Question

receives 100 mobile phones for repair on a particular week. 18 of
the phones are less than a year, 60 phones are more than a
year but less than 2 years and the rest are older than 2 years.
The company provides warranty for phones less than a year old.
Compute the probability that a phone chosen at random will
meet the following criteria:
a. Under warranty period
b. Older than 2 years
c. Less a year old or more than 2 years old
d. Not covered under warranty