Which of the following statements is incorrect with regard to gross profit or gross profit margin?

(a) The gross profit margin and cost of goods sold percentage are complements of each other.

(b) Generally, firms want to maintain the relationship between gross profit and sales, or, if possible, increase gross profit margin.

(c) The gross profit margin tends to be more stable in industries such as groceries.

(d) When cost of goods sold increases, most firms do not raise prices.