CREATE TABLE table_18409 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Result" TEXT, "Candidates" TEXT)

how many incumbent with district being tennessee 5
SELECT COUNT("Incumbent") FROM table_18409 WHERE "District" = 'Tennessee 5'
SELECT COUNT("Incumbent") FROM "table_18409" WHERE "District" = 'Tennessee 5'