Name the Wins which has a Class of 350cc, and a Year smaller than 1973?
CREATE TABLE "grand_prix_motorcycle_racing_results" (
  "year" real,
  "class" text,
  "team" text,
  "points" real,
  "wins" real
);
SELECT SUM("wins") FROM "grand_prix_motorcycle_racing_results" WHERE "class"='350cc' AND "year"<1973;