What is the mean level number when the example name is lower snake and the approximate number is hus is less than 370?
CREATE TABLE "united_states" (
  "name" text,
  "level" real,
  "digits" real,
  "average_size_square_miles" text,
  "number_of_h_us_approximate" real,
  "example_name" text,
  "example_code_huc" real
);
SELECT AVG("level") FROM "united_states" WHERE "example_name"='lower snake' AND "number_of_h_us_approximate"<370;