How Much Studying is required for SAT Lit and World History?

<p>I still don't know if I'm going to be taking SAT Subjects or if I will be focusing on ACT (depends on how my scores are for May SAT). If I decide to take the Subjects tests (I know about late registration) how much studying does Literature and World History require? I just finished up AP World and took the AP test, so how much more studying should I do? Thanks in advance!</p>