I assume you mean for one or two passengers, so the T2 would be enough. But the fare basis alone does not get you a ticket. In order to get the T fare, there must also be a published T fare between your origin and destination cities (which there might not be), and you must be booking a trip that falls within that T fare's restrictions (e.g., advance purchase, Saturday night stay, etc.). In your case, either the lowest published fare is S, or there is a T but you don't qualify.