For one growing season Farmer Smith hires 4 workers, and leases 2 tractors and 15 hectares of farmland and produces 120 000 bushels of crop. The next year he hires 8 workers, and leases 4 tractors and 30 hectares of farmland and produces 210 000 bushels of crop. This firm (the farmer) is exhibiting ________ returns to scale.
◦ decreasing
◦ increasing
◦ constant
◦ marginal
◦ variable