Step 1 :Calculate net sales by subtracting sales returns and allowances from sales revenue: \(205000 - 1900 = 203100\)
Step 2 :Calculate cost of goods sold (COGS) by starting with the beginning inventory, adding purchases and freight-in, subtracting purchase returns and allowances and purchase discounts, and then subtracting the ending inventory: \((36000 + 180000 + 3500 - 1000 - 1400) - 37000 = 180100\)
Step 3 :Calculate gross margin by subtracting COGS from net sales: \(203100 - 180100 = 23000\)
Step 4 :Final Answer: The net sales for Northern Windows for the year ended December 31, 2023 is \(\boxed{203100}\). The cost of goods sold is \(\boxed{180100}\). The gross margin is \(\boxed{23000}\)