Dear aspirant

At first congratulations for your result and wishes for your future life . You have not mentioned the name of the entrance where you got 40k rank in general category. Most probably it is JEE MAIN.

By Jee main JOSAA counselling you can some of NITs ( not the top departments of the topmost NITs , but many departments in the bottom list NITs ) .

And You said that you got CSE in Calcutta University. You should upgrade as by your choices because there are many chances for you to get every engineering departments in Jadavpur University except  CSE EE ECE IT etc.

So I think you should go for JU if you get departments like Mechanical engineering, chemical engineering , production engineering etc . If you miss that then you should choose NITs over calcutta University.

However you can check your chances here

Best wishes.