how much is fare and hours by taxi or bus to capital airport from Beijng Nanyuan airport??

I bought a plane ticket to Nanyuan airprt instead of PEK where i can take my international flight out of China. I will arrive at at 1430 pm and I am supposed to arrive Capital arprt at 2100 pm at night. How much is the fare, how many hours to capital arprt and what should i board as a means of transport for efficiency and time factor???
Thanks to any one who answers this. Have a great day