CREATE TABLE table_28607 ("Election number" FLOAT, "Election date" TEXT, "District" TEXT, "Province" TEXT, "Took office" TEXT, "Left office" TEXT)

What is the date in which a politician who left office on 1840-10-11 for a politician whose election number was 11?
SELECT "Left office" FROM table_28607 WHERE "Election number" = '11'
SELECT "Left office" FROM "table_28607" WHERE "Election number" = '11'