A poultry farmer keeps 500 layers. In one month, total eggs collected were 12,000, feed cost was ₦75,000, labour cost was ₦20,000, and miscellaneous expenses were ₦5,000. If eggs were sold at ₦50 each, what was the gross margin for that month?

Gross revenue = 12,000 × ₦50 = ₦600,000. Total variable costs = ₦75,000 + ₦20,000 + ₦5,000 = ₦100,000. Gross margin = ₦600,000 − ₦100,000 = ₦500,000. Option B (₦425,000) results from incorrectly subtracting only feed cost twice; option D (₦480,000) results from omitting miscellaneous expenses from revenue instead of cost.