A shop owner offers the following discount options on an article to a customer:

1. Successive discounts of 15% and 25%, and then pay a service tax of 12%

2. Successive discounts of 25% and 15%, and then pay a service tax of 12%

3. Pay a service tax of 12% first, then successive discounts of 25% and 15%

Which one of the following is correct?