Question: Which Quantity has an Axle arrangement of 2′C h2?
SQL: SELECT AVG("Quantity") FROM "2-18842985-3" WHERE "Axle arrangement" = '2′C h2';

Question: Which Year(s) of manufacture has an Axle arrangement of 2′B n2?
SQL: SELECT "Year(s) of manufacture" FROM "2-18842985-3" WHERE "Axle arrangement" = '2′B n2';