CREATE TABLE table_39470 ("Year" FLOAT, "Entrant" TEXT, "Chassis" TEXT, "Engine" TEXT, "Points" FLOAT)

What chassis is used in 1989 with a cosworth engine?
SELECT "Chassis" FROM table_39470 WHERE "Year" = '1989' AND "Engine" = 'cosworth'
SELECT "Chassis" FROM "table_39470" WHERE "Engine" = 'cosworth' AND "Year" = '1989'