Lampposts will be erected every [[$ 50 $]] meters on a 10-kilometer stretch of highway. The contractor retrieves three poles at a time from the warehouse by car, transports the poles to their correct places, and sets out to pick up the next batch. The warehouse is located immediately along the road, two kilometers before the start of the illuminated section. The work starts from the warehouse and ends there. How long does the contractor have to drive at the minimum? (Source: Finnish matriculation exam, spring 1999)



Answer: The contractor will have to drive at least km.