I would say, Mandarin is very helpful for emerging Chinese market, two years are good and you can learn more once you get in China. And since Russian has close business relationship especially with northen China, I would suggest you take that. The rest 3 options I would say, English can me more useful~~It's business in Asia, not Africa or Europe~And you can always use English as a tool for markets in Korea/HK/Singapore and Japan.
Good luck on your study!