CREATE TABLE table_57526 ("Class" CLOB, "Type" CLOB, "Introduced" CLOB, "Fleet Size" FLOAT, "Numbers" CLOB)

What is the average fleet size for the Shunter type introduced in 1959?
SELECT AVG("Fleet Size") FROM table_57526 WHERE "Type" = 'shunter' AND "Introduced" = '1959'
SELECT AVG("Fleet Size") FROM "table_57526" WHERE "Introduced" = '1959' AND "Type" = 'shunter'