CREATE TABLE table_79274 ("Class" CLOB, "Wheel arrangement" CLOB, "Fleet number ( s ) " CLOB, "Manufacturer" CLOB, "Year made" CLOB, "Quantity made" CLOB, "Quantity preserved" CLOB, "Year ( s )  retired" CLOB)

Which class had a quantity made of 20?
SELECT "Class" FROM table_79274 WHERE "Quantity made" = '20'
SELECT "Class" FROM "table_79274" WHERE "Quantity made" = '20'