- **Discount Calculation**: The marked price of the chain is Rs5,000. With a 15% discount, the selling price becomes Rs5,000 - (15% of Rs5,000) = Rs5,000 - Rs750 = Rs4,250.

- **Profit Condition**: The jeweller still makes a profit of 6.25% on the cost price. If C is the cost price, then C × 1.0625 = Rs4,250.

- **Finding Cost Price**: Solve for C: C = Rs4,250 / 1.0625 = Rs4,000.

- **Option 1**: Rs5,000 - This is the original marked price, not the cost price.

- **Option 2**: Rs4,400 - Incorrect cost price; does not satisfy profit condition.

- **Option 3**: Rs3,400 - Incorrect as it is less than the discounted price.

- **Option 4**: Rs4,000 - ✅ This is the correct cost price, meeting all conditions.

**YOUR ANSWER IS RIGHT**