The average distance that can be traveled with 1 liter of gasoline from the motorbike under investigation is 38 km with a standard deviation of 6 km. If the distance traveled is normally distributed:

a. What percentage of these motorbikes can only reach 30 km per use of 1 liter of petrol?
b. What percentage can reach between 25 km and 35 km?
c. 10% are said to be fuel efficient motorbikes. What is the minimum distance?