CREATE TABLE table_16324 ("Number Range" TEXT, "Builder" TEXT, "Introduced" FLOAT, "No. Built" FLOAT, "Region" TEXT, "Withdrawn" FLOAT)

What is the minimum introduced value for the Departmental region?
SELECT MIN("Introduced") FROM table_16324 WHERE "Region" = 'Departmental'
SELECT MIN("Introduced") FROM "table_16324" WHERE "Region" = 'Departmental'