What is the average population vlue for an area smaller than 26.69 square km and has an official name of Rogersville?
CREATE TABLE "communities" (
  "official_name" text,
  "status" text,
  "area_km_2" real,
  "population" real,
  "census_ranking" text
);
SELECT AVG("population") FROM "communities" WHERE "area_km_2"<26.69 AND "official_name"='rogersville';