What was the 2006 population for the local government area of alexandrina council whose rank was smaller than 19?
CREATE TABLE table_59540 (
    "Rank" real,
    "Local government area" text,
    "Population 2006 census" real,
    "Population 2007 estimate" real,
    "Growth rate" text,
    "Stat. division/district" text
)
SELECT AVG("Population 2006 census") FROM table_59540 WHERE "Local government area" = 'alexandrina council' AND "Rank" < '19'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: What was the 2006 population for the local government area of alexandrina council whose rank was smaller than 19? ### Input: CREATE TABLE table_59540 (
    "Rank" real,
    "Local government area" text,
    "Population 2006 census" real,
    "Population 2007 estimate" real,
    "Growth rate" text,
    "Stat. division/district" text
) ### Response: SELECT AVG("Population 2006 census") FROM table_59540 WHERE "Local government area" = 'alexandrina council' AND "Rank" < '19'