Calculate the gross profit percentages for each of the following situations and, based on these results, identify which situations are most preferable:

a. Sales of $500,000, cost of goods sold of $300,000

b. Sales of $600,000, gross profit of $300,000

c. Sales of $600,000, cost of goods sold of $250,000

d. Sales of $500,000, cost of goods sold of $100,000 E-967