Find the average ram mib size of the chip models that are never used by any phone.
CREATE TABLE chip_model (
    model_name text,
    launch_year number,
    ram_mib number,
    rom_mib number,
    slots text,
    wifi text,
    bluetooth text
)

CREATE TABLE screen_mode (
    graphics_mode number,
    char_cells text,
    pixels text,
    hardware_colours number,
    used_kb number,
    map text,
    type text
)

CREATE TABLE phone (
    company_name text,
    hardware_model_name text,
    accreditation_type text,
    accreditation_level text,
    date text,
    chip_model text,
    screen_mode text
)
SELECT AVG(ram_mib) FROM chip_model WHERE NOT model_name IN (SELECT chip_model FROM phone)
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: Find the average ram mib size of the chip models that are never used by any phone. ### Input: CREATE TABLE chip_model (
    model_name text,
    launch_year number,
    ram_mib number,
    rom_mib number,
    slots text,
    wifi text,
    bluetooth text
)

CREATE TABLE screen_mode (
    graphics_mode number,
    char_cells text,
    pixels text,
    hardware_colours number,
    used_kb number,
    map text,
    type text
)

CREATE TABLE phone (
    company_name text,
    hardware_model_name text,
    accreditation_type text,
    accreditation_level text,
    date text,
    chip_model text,
    screen_mode text
) ### Response: SELECT AVG(ram_mib) FROM chip_model WHERE NOT model_name IN (SELECT chip_model FROM phone)