Austin is comparing the prices of two truck rental companies. company a charges $4 per hour and an additional $70 as service charges. company b charges $5 per hour and an additional $60 as service charges. part a: write an equation to represent each company's total charges for renting a truck for a certain number of hours. for both equations (one for company a and one for company b), define the variable used. (4 points) part b: which company would charge less for renting a truck for 6 hours? justify your answer. (3 points) part c: how much money is saved by using the services of company b instead of company a to rent a truck for 7 hours? (3 points)