How many parties match the canididates listed as howard baker, sr. (r) 68.9% boyd w. cox (d) 31.1%?
CREATE TABLE table_18517 (
    "District" text,
    "Incumbent" text,
    "Party" text,
    "First elected" real,
    "Result" text,
    "Candidates" text
)
SELECT COUNT("Party") FROM table_18517 WHERE "Candidates" = 'Howard Baker, Sr. (R) 68.9% Boyd W. Cox (D) 31.1%'
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 parties match the canididates listed as howard baker, sr. (r) 68.9% boyd w. cox (d) 31.1%? ### Input: CREATE TABLE table_18517 (
    "District" text,
    "Incumbent" text,
    "Party" text,
    "First elected" real,
    "Result" text,
    "Candidates" text
) ### Response: SELECT COUNT("Party") FROM table_18517 WHERE "Candidates" = 'Howard Baker, Sr. (R) 68.9% Boyd W. Cox (D) 31.1%'