Jake is comparing the prices of two mattress cleaning companies. company a charges $30 per mattress and an additional $13 as service charges. company b charges $28 per mattress and an additional $15 as service charges.

part a: write an equation to represent each company's total charges for cleaning a certain number of mattresses. 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 cleaning 4 mattresses? justify your answer. (3 points)

part c: how much money is saved by using the services of company b instead of company a to clean 7 mattresses? (3 points)