What is Brown Motors best point total using the Offenhauser L4 engine since 1950?
CREATE TABLE "complete_formula_one_world_championship_" (
  "year" real,
  "entrant" text,
  "chassis" text,
  "engine" text,
  "points" real
);
SELECT MAX("points") FROM "complete_formula_one_world_championship_" WHERE "year">1950 AND "engine"='offenhauser l4' AND "entrant"='brown motors';