The mean amount of gasoline and services charged by Key refining Company credit customers is $70 per month.The distribution of amounts spent is approximately normal with a standard deviation of $10.

a)Compute the probability of selecting a credit card customer at random and finding the customer charged between $70 and $83 last month?

b)What is the probability that a particular customer charges less than $45?

c)If Key Refining decided to send a special financing plan to charge account customers having the highest 10% of the money charges. What is the dividing point between the customers who receive the special plan and those who do not?

Provide explanation please