A person drives 20,000 miles per year, using a car with a fuel efficiency of 20 miles per gallon of gasoline. Assuming that the average price of gasoline is $3.50 per gallon, how much money would this person save in a year by switching to a car with a fuel efficiency of 50 miles per gallon of gasoline?Sam typed 6 letters, each of which had either 1 or 2 pages. If Sam typed 10 pages in all, how many of the letters had 2 pages