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Well I must say it depends on a person. If he/ she is determinant or consistent then 10-12 days are more than enough (and this timeline is for those aspirants who do not know the ABC of this subject). Secondly i must say aspirants should not rely on books that are available in market (For me those books are useless and waste of money). Just make your own notes, read quality books and foreign authors and comprehend the topic. Soon you will fall in love with this subject.