Explanation:

- The trader's balance weighs 20% less, so when "1 kg" is sold, only 0.8 kg is actually given.

- The trader marks up goods but uses this faulty balance to gain extra profit.

- Let cost price (CP) of 1 kg = ?100.

- Marked price = ?x (to be found). Sells at marked price.

- Sells 0.8 kg, but gets paid for 1 kg (as per scale).

- Effective selling price per kg = Marked price.

- Real cost for 0.8 kg = 0.8 × ?100 = ?80.

- Profit = Selling Price (for 0.8 kg) - Cost (for 0.8 kg) = x - 80.

- Overall profit = 35% ? (x - 80)/80 = 0.35 ? x - 80 = 28 ? x = ?108.

- Mark­up = (Marked Price - Cost Price) / Cost Price × 100 = (108-100)/100 × 100 = 8%

- Correct option: Option:2, 8