CREATE TABLE table_57525 ("Class" TEXT, "Type" TEXT, "Introduced" TEXT, "Fleet Size" FLOAT, "Numbers" TEXT)

What is the year of introduction for the Electro-Diesel locomotive?
SELECT "Introduced" FROM table_57525 WHERE "Type" = 'electro-diesel locomotive'
SELECT "Introduced" FROM "table_57525" WHERE "Type" = 'electro-diesel locomotive'