Hey,

Since you are changing your stream there will a deduction of  2.5% to 5% maximum (depending from college to college ) from your best 4 percentage. 

For taking admission in BA (program) in DU Admissions, all five subjects will be considered while calculating the final percentage.If you don't  include subjects given in List A in 'best four' then you will have to face a deduction of 2.5 per cent for each subject.

Hope this helps.