environmental and resource economics

Consider a city council sewage system that produces bad smell ( S) which decreases with distance (d) in kilometers. As a manager of the sewage system, you are looking for a house as close to the sewage system as possible, and the perceived damage is $1 per unit of bad smell which is directly associated with the location of the house. The travel cost between your house and the sewage system is 4d one way. Write expression of total cost (TC) as a function of distance (d).