What is the mean number of wins for the norton team in 1966, when there are 8 points?
CREATE TABLE "motorcycle_grand_prix_results" (
  "year" real,
  "class" text,
  "team" text,
  "points" real,
  "wins" real
);
SELECT AVG("wins") FROM "motorcycle_grand_prix_results" WHERE "team"='norton' AND "year"=1966 AND "points"=8;