Explanation:

- The article's selling price is Rs 4,800 with a 20% profit.

- The cost price can be calculated as:

$$\text{Cost Price}=\frac{\text{Selling Price}}{1+\text{Profit Percentage}}=\frac{4,800}{1.20}=4,000.$$

- When the selling price increases by Rs 600, the new selling price is Rs 5,400.

- The new profit amount is $$5,400-4,000=1,400.$$

- The profit percentage with the new selling price is:

$$\frac{1,400}{4,000}\times 100=35\mathrm{\%}.$$

Option 4: 35% is correct.