What is the smallest point amount for years prior to 1958 when the class is 350cc?
CREATE TABLE "motorcycle_grand_prix_results" (
  "year" real,
  "class" text,
  "team" text,
  "points" real,
  "wins" real
);
SELECT MIN("points") FROM "motorcycle_grand_prix_results" WHERE "year"<1958 AND "class"='350cc';