Sarah wants to buy the car that has a better mileage rating. Cars of Company A travel 20 miles per gallon and cars of Company B travel 14 km per liter.
[1 mile = 1.6 km; 1 gallon = 3.79 liters]
Part A: Which company's car should Sarah buy? Justify your answer by comparing the mileages after converting to the same units.
Part B: If 10 gallons of gas is filled in the car which gives better mileage, and you went on a drive and checked on the gas used every 30 miles, describe appropriate scales on the x-axis and y-axis to graph the rate at which the car uses gas.