The Energy Information Administration reported that the mean retail price per gallon of regular grade gasoline was $2.81 (Energy Information Administration, November 2010). Suppose that the standard deviation was $.10 and that the retail price per gallon has a bellshaped distribution.
a. What percentage of regular grade gasoline sold between $2.71 and $2.91 per gallon?
b. What percentage of regular grade gasoline sold between $2.71 and $3.01 per gallon?
c. What percentage of regular grade gasoline sold for more than $3.01 per gallon?