calculating cost

Ok.

for a car allocated to a “commercial” car category, Sale price of $27,990, the total advertising cost should come out to be $1125.

Sale price is over 25k therefore duration is 2 a week for state 1 a week for Local
Commercial is a 5 line Advertisement
5 Line prices are: 50 and 60 for local (two types of local papers) and 80 and 65 for State (again 2 types of state papers) there's a 100 web advertising fee and a 225 magazine advertising fee for commercial category cars

The data is in the Advertsing spreadsheet i provided in OP.