CREATE TABLE table_70406 ("Year" FLOAT, "Entrant" CLOB, "Chassis" CLOB, "Engine" CLOB, "Points" FLOAT)

How many years was ensign n180b a Chassis with 4 points?
SELECT SUM("Year") FROM table_70406 WHERE "Points" = '4' AND "Chassis" = 'ensign n180b'
SELECT SUM("Year") FROM "table_70406" WHERE "Chassis" = 'ensign n180b' AND "Points" = '4'