What is the average Isolation in the municipality of Sunndal at an elevation of more than 1850?
CREATE TABLE "see_also" (
  "peak" text,
  "elevation_m" real,
  "prominence_m" real,
  "isolation_km" real,
  "municipality" text,
  "county" text
);
SELECT AVG("isolation_km") FROM "see_also" WHERE "municipality"='sunndal' AND "elevation_m">1850;