Bus from Yuanyang to Kunming

Hello, I always find the bus schedule from Kunming to Yuanyang but not the reverse. Can you let me know what's the earliest bus departing Yuanyang?
I'd like to reach in Kunming on time to catch the flight at 17:50 from Kunming to Guilin. Would that be possible? By the way, my trip will be in mid-december.