CREATE TABLE table_74830 ("Wheel arrangement" TEXT, "Manufacturer Serial numbers" TEXT, "Year introduced MRWA" TEXT, "Quantity made" TEXT, "Quantity preserved" TEXT, "Year ( s )  withdrawn" TEXT)

What was the year the MRWA with a wheel arrangement of 4-6-2 was introduced?
SELECT "Year introduced MRWA" FROM table_74830 WHERE "Wheel arrangement" = '4-6-2'
SELECT "Year introduced MRWA" FROM "table_74830" WHERE "Wheel arrangement" = '4-6-2'