CREATE TABLE "1850_1871" (
  "class" text,
  "wheel_arrangement" text,
  "manufacturer" text,
  "year_made" text,
  "quantity_made" text,
  "quantity_preserved" text,
  "year_s_withdrawn" text
);

Question: What year was class of undine?
SQL: SELECT "year_made" FROM "1850_1871" WHERE "class"='undine';

Question: What was the quantity preserved for quantity made of 15?
SQL: SELECT "quantity_preserved" FROM "1850_1871" WHERE "quantity_made"='15';

Question: Name the year for hercules
SQL: SELECT "year_made" FROM "1850_1871" WHERE "class"='hercules';