CREATE TABLE table_68548 ("Year" FLOAT, "Chassis" TEXT, "Engine" TEXT, "Start" TEXT, "Finish" TEXT, "Entrant" TEXT)

What is the chassis for offy engine and 25th finish?
SELECT "Chassis" FROM table_68548 WHERE "Engine" = 'offy' AND "Finish" = '25th'
SELECT "Chassis" FROM "table_68548" WHERE "Engine" = 'offy' AND "Finish" = '25th'