How much time does preparing for SAT II Chemistry & Biology take?

I’m thinking about taking the SAT II Chemistry & Biology in June. I’ll be taking the SAT I in May. Would one month (May) be enough to prepare for both Chemistry & Biology? I’m aiming for 700+ minimum, 750+ ideally on both.

I have the PR Biology, Barron’s Chemistry, and the Blue Subject Book. For biology, I probably know about 30% of the content needed (according to the PR Biology book) and for chemistry, I probably know about 60-70% of the content needed (according to Barron’s Chemistry). When I mean “know,” I mean that I’ve done the topics before in school - I’ll probably needed to review them though.

Is one month sufficient to get a 750+ in both? I could probably spend 3-4 hours on each subject every week. Should I be spending more time each week from the start of May to the start of June?

Note: I’m an international student. I don’t do AP Chemistry/Biology. I am taking the Biology and Chemistry classes offered in my school though.

Also, would you guys recommend taking just one SAT Subject exam or two? I’ve already taken Math Level 2 and gotten a score I’m happy with. All the schools I’m applying ask for two SAT Subject exams. Though, for some odd reason, I get the feeling that submitting three might help my application (assuming I do well in Biology & Chemistry) - I am an international student from Australia, and perhaps colleges might not be familiar with our curriculum? Is it really worth doing an extra SAT Subject exam? In my case, I’d probably drop Biology. I’m looking to major in something biology-chemistry related.

Take 2.
Ideally, 2 hours a day for a week before the exam should get you a 700+.
I’m an international student as well, and I only studied a week before the exam and got a 730.

Thanks @DarkEclipse. I think I’ll just do the SAT Chemistry in June. I want to try to get a 750+ (ideally 800), so I think focusing on just one subject test would be better. What book(s) did you use?

Barron’s, although PR is better. I should have used PR, because Barron’s contains a LOT of extra information, and it is not good for revision in a short amount of time.

Is this for Chemistry?

Biology.
Although PR for Chemistry is fine too.

Ah, okay. Have you taken the SAT Chemistry?
If yes, which one would you say is harder? And which one took more time to prepare for?

No, I will, but comparing my prep between the two, I’d say Chemistry is definitely easier, has a more lenient curve, but takes an equal amount of time to prep.

Thank you so much for your help!

No problem. Good luck!