Willie lohmann travels from city to city in the conduct of his business. every other year he buys a used car for about $15,000. the auto dealer allows about $8000 as a trade-in allowance, with the res

Willie lohmann travels from city to city in the conduct of his business. every other year he buys a used car for about $15,000. the auto dealer allows about $8000 as a trade-in allowance, with the result that salesman willie spends $7000 every other year for a car.