The Energy Information Administration reported that the mean retail price per gallon of regular grade gasoline was $3.43 (Energy Information Administration, July 2012). Suppose that the standard deviation was $.10 and that the retail price per gallon has a bell-shaped distribution.
a. What percentage of regular grade gasoline sold between $3.33 and $3.53 per gallon?
b. What percentage of regular grade gasoline sold between $3.33 and $3.63 per gallon?
c. What percentage of regular grade gasoline sold for more than $3.63 per gallon?