Tell me the average Laps for grid larger than 12 and bikes of ducati 999rs for dean ellison
CREATE TABLE "superbike_race_2_classification" (
  "rider" text,
  "bike" text,
  "laps" real,
  "time" text,
  "grid" real
);
SELECT AVG("laps") FROM "superbike_race_2_classification" WHERE "grid">12 AND "bike"='ducati 999rs' AND "rider"='dean ellison';