How many of the schools are designated private/Presbyterian?
CREATE TABLE table_15915 (
    "School" text,
    "Location" text,
    "Founded" real,
    "Affiliation" text,
    "Enrollment" real,
    "Team Nickname" text,
    "Primary conference" text
)
SELECT COUNT("Location") FROM table_15915 WHERE "Affiliation" = 'Private/Presbyterian'
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: How many of the schools are designated private/Presbyterian? ### Input: CREATE TABLE table_15915 (
    "School" text,
    "Location" text,
    "Founded" real,
    "Affiliation" text,
    "Enrollment" real,
    "Team Nickname" text,
    "Primary conference" text
) ### Response: SELECT COUNT("Location") FROM table_15915 WHERE "Affiliation" = 'Private/Presbyterian'