In 2020, Oxford Inc. used 24,400 pounds of plastic (direct materials) to produce 8000 units as opposed to 2021 when Oxford produced 8500 units using 32,400 pounds of plastic. The type of plastic Oxford uses cost $10 per pound in 2020 and rose to $10.50 per pound in 2021. In comparing results for these two years, what would be the cost effect of growth for the plastic material?