What is the mean number of laps where Time/retired was a water leak and the grid number was bigger than 12?
CREATE TABLE "race" (
  "driver" text,
  "constructor" text,
  "laps" real,
  "time_retired" text,
  "grid" real
);
SELECT AVG("laps") FROM "race" WHERE "time_retired"='water leak' AND "grid">12;