Conversation so far:
what is the total number of passenger coaches owned by indian railways
As of March 2017, Indian Railways' rolling stock includes 70,937 passenger coaches.
Who is the minister of the Indian railways system
Piyush Vedprakash Goyal (born 13 June 1964) is an Indian politician and the current minister of Railways and Commerce in the Government of India.

Question: what is the annual revenue of the system
Self-contained rewrite: what is the annual revenue of the Indian Railways system