What is the Grade that has Turf 1600m?
CREATE TABLE "step_races" (
  "race_name" real,
  "grade" text,
  "racecourse" text,
  "distance" text,
  "priority_entry_rights_to_derby" text
);
SELECT "grade" FROM "step_races" WHERE "priority_entry_rights_to_derby"='turf 1600m';