CREATE TABLE table_55002 ("Year" TEXT, "Make & Model" TEXT, "Length" TEXT, "Engine Type" TEXT, "Numbers" TEXT)

If length is ft (m) with numbers of 6600-6684 (84 buses) for 2003, what is the engine type?
SELECT "Engine Type" FROM table_55002 WHERE "Length" = 'ft (m)' AND "Year" = '2003' AND "Numbers" = '6600-6684 (84 buses)'
SELECT "Engine Type" FROM "table_55002" WHERE "Length" = 'ft (m)' AND "Numbers" = '6600-6684 (84 buses)' AND "Year" = '2003'