Which engine of bmw had the lowest points and chassis of march 792 that is newer than 1979?
CREATE TABLE "complete_european_formula_two_championsh" (
  "year" real,
  "entrant" text,
  "chassis" text,
  "engine" text,
  "points" real
);
SELECT MIN("points") FROM "complete_european_formula_two_championsh" WHERE "engine"='bmw' AND "chassis"='march 792' AND "year">1979;