30. The Energy Information Administration reported that the mean retail price per gallon of regular grade gasoline was $2.30 (Energy Information Administration, February 27, 2006).

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 $2.20 and $2.40 per gallon?

b. What percentage of regular grade gasoline sold between $2.20 and $2.50 per gallon?

c. What percentage of regular grade gasoline sold for more than $2.50 per gallon?