If an engine, usually driven at speed of 60 miles per, had a lifespan of 30000 miles, what will be the lifespan of an engine which is usually driven at a speed of 40 miles per hour?
Given that the normal lifespan of an engine is 60,000 miles, what was the lifespan of an engine, which was driven for 20000 miles at a speed of 60 miles per hour and later at a speed of 40 miles per hour?