Add a ringtone (from res/raw) to android system ringtones

Question

I have an app that runs on a custom android tablet. I want to add a ringtone that I would include in res/raw folder and the app should copy it to system ringtones folder. I have root access.

I would like it to be over written in case if a ringtone with same name exists.

I tried to google for it but couldn't get any help

UPDATE

I have tried this code but it the file isn't moved/copied

try{

        InputStream ins = getResources().openRawResource(
                getResources().getIdentifier("ring_default",
                        "raw", getPackageName()));
        Process process = Runtime.getRuntime().exec("su");
        DataOutputStream out = new DataOutputStream(process.getOutputStream());
        out.writeBytes("mount -o remount,rw /system\n");
        out.writeBytes("mv "+ins.toString()+" /system/file.new\n");
        out.writeBytes("exit\n");
        out.flush();
        process.waitFor();
    } catch (InterruptedException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

Update 2 i tried out.writeBytes("mv /system/media/audio/ringtones/ring4.wav /system/media/audio/ringtones/ring5.wav\n"); and it works.

Now I need to know how I can find the path to my res/raw folder and replace it in the above case.

Thanks in advance!