When purchase costs of inventory regularly decline which method of inventory costing will yield the lowest gross profit and income?

When purchase costs of inventory regularly decline, the Last-In, First-Out (LIFO) method of inventory costing will yield the lowest gross profit and income. This is because LIFO assumes that the most recently purchased inventory (which is cheaper in this scenario) is sold first, resulting in higher cost of goods sold (COGS) and lower gross profit. Consequently, this leads to a reduced net income compared to other methods like First-In, First-Out (FIFO) or weighted average cost.