Explanation:

- Scenario: A shopkeeper uses 940 gm instead of 1 kg to weigh goods.

- Selling Strategy: Sells this 940 gm with a marked 4% profit on the price for 1 kg.

- Profit Calculation: Actual weight is light by 60 gm per kg, which gives him extra profit.

- Cost Analysis: The shopkeeper sells 940 gm as if it were 1 kg and marks a 4% profit.

- Actual Profit Percentage Calculation:

- Without tampering, profit from 1 kg = 4%.

- Adjust for the reduced weight (940 gm instead of 1000 gm).

- Actual increased profit from reduced weight = $(1000/940)-1$ = 6.38%.

- Total profit = 4% (advertised) + 6.38% = 10.64%.

- Answer: Option 3 – 10.64% is correct.