Checking random dates later this month, the only flight from MIA to LAX operated by a wide-body aircraft is AA960, which is flown by a "77W-Boeing 777" aircraft. 77W is the equipment code for the 777-300ER. If you were to check the seat map for your flight, it should show two rows in F and thirteen in J (business). The 777-200 had no first class cabin and ten rows in J (often sold as F for domestic flights).