Shaver Manufacturing, Inc., provides dental insurance to its employees. A recent study by human resource director shows the annual cost per employee each year followed the normal probability distribution, with the mean of $1,280 and a standard deviation of $420 per year.
1. What fraction of employees cost more than $1,500 per year for the dental expenses?
2. What fraction of employees cost between $1,500 and $2,000 per year?
3. Determine the percent that didn't have any dental expense.
4. What was the cost for 10% of employees who incurred highest dental expense?