Hey Anu,

To be very honest, it's all upto you. B Phar is indeed a good subject and you have to study in depth therefore you have to put in some time everyday. 

Well, it also depends on how fast you memorize things. If you're fast then it'll be easier for you hence, you'll require less time and vice versa if you're a slow learner. 

You capability and caliber marks this line of interest. Study enough that you're confident with yourself. Good luck!