In app purchase help

I tried to add billing permission to my android manifest but whenever I try to build my app it gives this error : Error building Player: XmlException: Multiple document element was detected. file:///C:/Users/Shay/Documents/FlappyBirdTest/Assets/Plugins/Android/AndroidManifest.xml Line 31, position 6. This is the xml file: All i did was add the billing thing at the end... how do I allow it to have in app purchases?