What is the average number of casualties for the convoy with a number of U-844?
CREATE TABLE table_49185 (
    "Date" text,
    "Number" text,
    "Type" text,
    "Captain" text,
    "Casualties" real
)
SELECT AVG("Casualties") FROM table_49185 WHERE "Number" = 'u-844'
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 is the average number of casualties for the convoy with a number of U-844? ### Input: CREATE TABLE table_49185 (
    "Date" text,
    "Number" text,
    "Type" text,
    "Captain" text,
    "Casualties" real
) ### Response: SELECT AVG("Casualties") FROM table_49185 WHERE "Number" = 'u-844'