how much would it cost for a single entry three month visa to the Chinese Embassy Costa Rica?

Hi I am an Australain citzen. If I post my chinese visa application to the Chinese Embassy Costa Rica can they process it. Also how much would it cost Im applying for a single entry three month visa and how long will it take. I´m staying with a host family i would like to get it posted there. Im only staying if Costa Rica for three weeks. I´m in Africa for one month before going to China in July. I do not trust Africa´s mailing system. Thank you