CREATE TABLE "24_hours_of_le_mans_results" (
  "year" real,
  "team" text,
  "co_drivers" text,
  "class" text,
  "laps" real,
  "pos" text,
  "class_pos" text
);

Question: What was the year of the finish with the class pos of 6th and laps smaller than 317?
SQL: SELECT SUM("year") FROM "24_hours_of_le_mans_results" WHERE "class_pos"='6th' AND "laps"<317;