The Energy Information Administration reported that the mean retail price per gallon of regular grade gasoline was $2.05 (Energy Information Administration, May 2009). 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 $1.95 and $2.15 per gallon?
b. What percentage of regular grade gasoline sold between $1.95 and $2.25 per gallon?
c. What percentage of regular grade gasoline sold for more than $2.25 per gallon?