Name the number of virtual for NBC
CREATE TABLE table_19453 (
    "Virtual" real,
    "Physical" real,
    "Call sign" text,
    "Branding" text,
    "Network" text,
    "Owner" text
)
SELECT COUNT("Virtual") FROM table_19453 WHERE "Network" = 'NBC'
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: Name the number of virtual for NBC ### Input: CREATE TABLE table_19453 (
    "Virtual" real,
    "Physical" real,
    "Call sign" text,
    "Branding" text,
    "Network" text,
    "Owner" text
) ### Response: SELECT COUNT("Virtual") FROM table_19453 WHERE "Network" = 'NBC'