CREATE TABLE table_22120 ("District" TEXT, "Incumbent" TEXT, "Party" TEXT, "First elected" FLOAT, "Results" TEXT, "Candidates" TEXT)

How many categories of first elected are in Washington 4 district?
SELECT COUNT("First elected") FROM table_22120 WHERE "District" = 'Washington 4'
SELECT COUNT("First elected") FROM "table_22120" WHERE "District" = 'Washington 4'