tanuja paduka is the best book for sm
so dnt worry just keep practising
i just read 5 chapters from paduka in sm
and secured 59 keeping the fact that i had attended only 35 marks questions in IT
SO u are on the right path
i must advise u one thing that dont worry for casestudies
take them as unseen passeges which we used to solve in cbse boards
just learn all the 6 chapters from paduka and surely u will come with flying colors