CREATE TABLE table_51685 ("Name" TEXT, "Rank" TEXT, "Years until mandatory retirement" TEXT, "Appointed by" TEXT, "Year appointed" FLOAT)

what rank has years until mandatory retirement of 6 years?
SELECT "Rank" FROM table_51685 WHERE "Years until mandatory retirement" = '6 years'
SELECT "Rank" FROM "table_51685" WHERE "Years until mandatory retirement" = '6 years'