Find Probability values for the normal distribution.
The mean amount of gasoline and services charged by Key Refining Company credit customers is $70 per month. The distribution of amounts spent is around normal with a standard deviation of $10.
[a] work out the probability of selecting a credit card customer at random and finding the customer charged between $70 and $83 last month.
[b] Calculate the probability of customers charging between $57 and $83 per month.
[c] Key Refining decided to send a special financing plan to charge account customers having the highest 10 percent of the money charges. What is the dividing point between customers who receive the special plan and those who do not?