human
Considering the provided database schema and associated query, produce SQL code to retrieve the answer to the query. 
###Database Schema: Railroad (quantity), Class, Road numbers, Builder, Build year
###Question: what is the road numbers when the builder is alco, the railroad (quantity) is union pacific railroad (105) and the class is csa-2?
gpt
SELECT Road numbers FROM table WHERE Builder = alco AND Railroad (quantity) = union pacific railroad (105) AND Class = csa-2