A car servicing station is running a special offer. The breakdown of the cost for different services is given below. Membership Fee: $50 (one-time cost) Air Freshener Cost: $4 per car per month Washing Cost: $10 per car per month Tire Replacement Cost: $400 per car Tire Pressure Check Cost: $15 per month The total cost for 12 months of this service for n cars is given by the expression below. Which statement best describes the constant in the expression?