What is the number for t c (k) when the notation is tl-2212?
CREATE TABLE table_15973 (
    "Formula" text,
    "Notation" text,
    "T c (K)" real,
    "No. of Cu-O planes in unit cell" real,
    "Crystal structure" text
)
SELECT COUNT("T c (K)") FROM table_15973 WHERE "Notation" = 'Tl-2212'
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 number for t c (k) when the notation is tl-2212? ### Input: CREATE TABLE table_15973 (
    "Formula" text,
    "Notation" text,
    "T c (K)" real,
    "No. of Cu-O planes in unit cell" real,
    "Crystal structure" text
) ### Response: SELECT COUNT("T c (K)") FROM table_15973 WHERE "Notation" = 'Tl-2212'