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 equations to represent Company A's and Company B's total mattress cleaning charges for a certain number of mattresses. Define the variable used in the equations. (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?