CREATE TABLE "iron_coaches" (
  "class_to_1928" text,
  "class_from_1928" text,
  "seats" text,
  "quantity" real,
  "year_s_of_manufacture" text,
  "remarks" text
);

Question: What is the average quantity for coaches manufactured in 1921/23, and had 40 seats?
SQL: SELECT AVG("quantity") FROM "iron_coaches" WHERE "year_s_of_manufacture"='1921/23' AND "seats"='40';

Question: Which class to 1928 value had years of manufacture of 1921/23 and class from 1928 of BCi-21?
SQL: SELECT "class_to_1928" FROM "iron_coaches" WHERE "year_s_of_manufacture"='1921/23' AND "class_from_1928"='bci-21';

Question: What is the smallest quantity having a Class to 1928 of BDi-21?
SQL: SELECT MIN("quantity") FROM "iron_coaches" WHERE "class_to_1928"='bdi-21';

Question: Which class from 1928 had a class to 1928 of BDi-21?
SQL: SELECT "class_from_1928" FROM "iron_coaches" WHERE "class_to_1928"='bdi-21';

Question: What were the remarks for the coach having a class from 1928 of Cid-21B?
SQL: SELECT "remarks" FROM "iron_coaches" WHERE "class_from_1928"='cid-21b';