Question

A large governmental survey of dental care among children 2 to 17 years old found the following distribution of times since last visit to the dentist:
(1st column)Time since last visit
(1st column)6 months or less
(1st column)>6 months but no more than 1 year
(1st column)>1 year but no more than 2 years
(1st column)>2 years but no more than 5 years
(1st column)More than 5 years

(2nd Column)Probability
(2nd Column).57
(2nd Column).18
(2nd Column).08
(2nd Column).03
(2nd Column) ?

Questions:
(a) What must be the probability that a child has seen a dentist in more than 5 years? _________
(b) What is the prob. that a randomly chosen child has not seen a dentist within the last 6 months? __________
(c) What is the probability that the child has seen a dentist within one year? _____________