20. After visiting Mountain State University during spring break, Meredith rents a car for 1 day to travel around the area. She has $100 to spend on car rental. Green Tree Car Rental charges $50 per day and $0.25 per mile. Big Rock Car Rental charges $60 per day and $0.20 per mile. Which company, if either, allows her to travel more miles, and how many miles more ?

(Note: Taxes are already included in the rental charges. )