Explanation:

- The ratio of the selling price (SP) to the cost price (CP) of the computer is given as 7:5.

- This means for every 5 units of cost price, the selling price is 7 units.

- To find the profit percentage, we calculate the profit, which is the difference between SP and CP.

- Profit = SP - CP = 7 units - 5 units = 2 units.

- Profit percentage is calculated as: (Profit/CP) × 100 = (2/5) × 100 = 40%.

- Option 3: 40% is the correct profit percentage.

Your answer is right.