Question: What is the build date of the model with PRR Class BRS24?
SQL: SELECT "Build date" FROM "2-1140522-2" WHERE "PRR Class" = 'BRS24';

Question: How many total units were built of Model DS-4-4-660 with a B-B wheel arrangement and a PRR Class of BS6?
SQL: SELECT SUM("Total produced") FROM "2-1140522-2" WHERE "Wheel arrangement" = 'B-B' AND "PRR Class" = 'BS6' AND "Builder’s Model" = 'DS-4-4-660';

Question: What is the build date of the model with a PRR Class of BRS24?
SQL: SELECT "Build date" FROM "2-1140522-2" WHERE "PRR Class" = 'BRS24';