A person has some stock of sugar. he marks 40% more than cost price on his stock. 20% of total stock he sells at 25% discount. 25% of remaining stock he sells at 20% discount. he sells 50% of remaining stock at 50% discount and remaining at marked price. What is his final gain/loss?

Assume 100 units at CP 100 each (total CP = 10000). MP = 140 per unit. 20% (20 units) sold at 25% discount: SP = 140×0.75 = 105 per unit. 25% of remaining 80 = 20 units sold at 20% discount: SP = 140×0.8 = 112. 50% of remaining 60 = 30 units sold at 50% discount: SP = 70. Remaining 30 units at MP 140. Total revenue = (20×105) + (20×112) + (30×70) + (30×140) = 2100 + 2240 + 2100 + 4200 = 10640. Gain = (10640-10000)/10000 = 6.4%. Option D is correct.