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

$\backslash$table$[[$Age$,$Number of Customers$],[20,59],[21-30,61],[31-40,97],[41-50,69],[51-60,88],[>60,68]]$

One customer is chosen at random for a prize giveaway.

Answer the following questions using either a fraction or a decimal rounded to three places.

a$.$ What is the probability that the customer is older than $30$ but no older than $60?$

b$.$ What is the probability that the customer is either older than $50$ or no more than $20?$

c$.$ What is the probability that the customer is older than $50?$