The following data for the years ended December 31, 2019 and 2020 were presented to the management Zigzag Company: 2020 = Net sales: 1,363,000, Cost of Sales: 911,800, Gross Profit: 451,200; 2019 =...

The following data for the years ended December 31, 2019 and 2020 were presented to the management Zigzag Company: 2020 = Net sales: 1,363,000, Cost of Sales: 911,800, Gross Profit: 451,200; 2019 = Net Sales: 1,250,000, Cost of Sales: 776,000, Gross Profit: 474,000. The management requested you to determine the cause of the decline in gross profit on sales in spite of the favorable information given by the sales division that the quantity sold in 2020 was higher than in 2019 and that the production costs in 2020 were lower than that of 2019 by 6%. The increase (decrease) in net sales due to cost factor is