Greetings Mahak!

Hope you're doing great.

Bharat Heavy Electricals Limited has given the notification for 145 trainee vacancy. BHEL has given both engineer and executive trainee vacancies for Mechanical, Civil, Electrical, Chemical, Finance & HR.BHEL executive trainee exam is CBT(Computer Based Examination). The examination has two papers: Professional paper(finance in your case) and Aptitude paper.

For more details regarding the examination please, follow this page: 

https://university.careers360.com/articles/how-get-job-at-bhel

I assume you must have gone through the details. Now coming back to your question, these are the books which you can refer for the preparation:

• Guide BHEL Finance (Engineer Trainees): https://www.amazon.in/Guide-BHEL-Finance-Engineer-Trainees/dp/818355329X
• Study Guide BHEL Engineer Trainees Electrical Engineering (Includes Technical And Non-technical Sections) By G.K.P
• Guide To BHEL Mechanical Engineering (Engineer Trainee) By Mittal

Hope this will help. Do reach out in the comment section below for more query.

All the best!

Cheers!