Explanation:

- Let the cost price of the table be \( T \).

- The cost price of a chair is 25% less than that of the table, so it is \( 0.75T \).

- The cost price for 5 chairs = \( 5 \times 0.75T = 3.75T \).

- The selling price for 5 chairs is the cost price of 7 tables = \( 7T \).

- Profit = Selling Price - Cost Price = \( 7T - 3.75T = 3.25T \).

- Profit percentage = \(\left(\frac{3.25T}{3.75T}\right) \times 100 = \left(\frac{3.25}{3.75}\right) \times 100 \approx 86.67\%\).

Option 3: 86.66 is correct.