i got 4928 rank in amrita where will i get a seat

Congratulations for your result. You know the cutoffs depend on various factors so it keeps changing every year. Youbhaven't mentioned which State you belong to, as the cutoffs also depend on that. Considering you as a general category student, you can expect
CS in both Amrithapuri and Bangalore Campuses as the closing ranks for these two campuses in Computer Science and Engineering lies around 6700 to 6900 rank for other state candidates. So both are achievable with this rank.
Rather you may get all the branches in Amrithapuri and Bangalore campus.
In Coimbatore campus, through Open quota you can get Aerospace Engineering, Civil engineering, Chemical, Electronics and Instrumentation Engineering.
Now this is based on previous years' data and this year the cutoffs might change. You can see the cutoffs for all campuses for all branches http://engineering.careers360.com/articles/aeee-cutoff