Explanation:

- The sofa's initial price is Rs24,000, and the sales tax on it is Rs1,200.

- To find the percentage of sales tax, we use the formula: (Sales Tax / Price Before Tax) x 100.

- In this case, (1,200 / 24,000) x 100 equals 5%.

- Option 1, 5%, matches this calculation precisely.

- Other options:

- Option 2, 6%, suggests a higher tax that would result in Rs1,440 as sales tax.

- Option 3, 8%, implies a larger sales tax of Rs1,920.

- Option 4, 4%, means a lower tax causing Rs960 as sales tax.

- The calculations confirm that the correct option is 1 - 5%.