Question $20$

A store manager gathers some demographic information from the store's customers. The following chart summarizes the age$-$related information they collected:

$\backslash$table$[[$Age$,$Number of Customers

One customer is chosen at random for a prize giveaway. $($Round answers to $4$ decimal places.$)$

a$.$ What is the probability that the customer is at least $20$ but no older than $49?$

b$.$ What is the probability that the customer is either older than $59$ or younger than $40?$

c$.$ What is the probability that the customer is at least $50?$