Let's start by figuring out how many games were played and how many points could've been scored.
Since each team plays each other team exactly once, we have (5 choose 2) or 5!/(2!*3!) or 10 total games. (You can also find this pretty quickly by hand: GH, GJ, GK, GL, HJ, HK, HL, JK, JL, and KL.)
If every game was a tie, we'd have 10 points. If every game had a winner, we'd have 30 points. Hence our point total, whatever it is, must be between 10 and 30.
S1 tells us that Team L finished with 8 points, which must represent TWO wins and TWO draws. This means that Team L was undefeated, so there can't be a team that won all four of its games. We could still have a team that won THREE games and tied with Team L, however, so S1 is INSUFFICIENT.
S2 tells us the total number of points, but not how many points Team L received. INSUFFICIENT!
Taking the two statements together, let's suppose that Team L does NOT have the highest total. That means some other team must have won THREE games. Since Team L won two and drew two, that means we have at least 5 games with a winner and at least 2 games with a draw.
Each win is worth 3 points and each draw is worth 2 points (one to each team), so 5 wins and 2 draws gives us 5*3 + 2*2 = 19 points. That means the other THREE games (we have 10 total) must have contributed a total of 4 points. But this is impossible!! Those games either had a winner (3 points) or a draw (2 points), so they contributed a minimum of 6 points (if all three games were draws) and a maximum of 9 points (if all three had a winner).
Hence no team could've scored more than Team L did, and the two statements together are SUFFICIENT.
