I need help on this question. Toby's Trucking Company determined that on an annual basis, the distance traveled per truck is normally distributed, with a mean of 50,000 miles and a standard deviation...

I need help on this question.

Toby's Trucking Company determined that on an annual basis, the distance traveled per truck is normally distributed, with a mean of 50,000 miles and a standard deviation of 12,000 miles.

1. 
   
   
   
   1. What proportion of trucks can be expected to travel between 38,000 and 62,000 miles in the year?
   
   
   2. What percentage of the trucks travel less than 35,000 miles in the year?
   
   
   3. What percentage of the trucks travel more than 57,000 miles in the year?
   
   
   4. How many miles will be traveled by at least (equal to and more than) 72% of the trucks?