Showing json using php into android studio textview

cant show the total amount of this equation using php which is json encoded to a textview in android studio

here is the equation in php

$d=2;
$d0=(($b1*2*9)+($b2*3) + (4*$b3))-(($b1*4*3)+($b2*9)+(2*$b3));
$d1 = (($b1 * 4) + ($b2 * 9) + ($b3)) - (($b1 * 9) + ($b2) + (4 * $b3));
$d2 = (($b1 * 3) + ($b2) + (2 * $b3)) - (($b1 * 2) + ($b2 * 3) + ($b3));
$a0 = $d0 / $d;
$a1 = $d1 / $d;
$a2 = $d2 / $d;
$tot = $a0 + ($a1 * 4) + ($a2 * 16);
$format = new \stdClass();
$format->predicted=number_format($tot, 2);
$json = json_encode($format);
echo $json;

Note* $b1, $b2 and $b3 are data from mysql.

The output is this

{"predicted":"35,370,362.30"}

now the code in android studio which is getting the string predicted in json is this. the code is working on my other module tho. I think the php file has the problem her

public GetTextViewData(Context context)
    {
        this.context = context;
    }

    @Override
    protected void onPreExecute()
    {
        super.onPreExecute();
    }

    @Override
    protected Void doInBackground(Void... arg0)
    {

        HttpClient myClient = new DefaultHttpClient();
        HttpPost myConnection = new HttpPost("http://10.0.2.2/sample/prediction.php");

        try {
            response = myClient.execute(myConnection);
            str = EntityUtils.toString(response.getEntity(), "UTF-8");

        } catch (ClientProtocolException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }


        try{
            JSONArray jArray = new JSONArray(str);
            json = jArray.getJSONObject(0);



        } catch ( JSONException e) {
            e.printStackTrace();
        }

        catch (Exception e)
        {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        return null;
    }
    protected void onPostExecute(Void result)
    {
        try {
            tv1.setText(json.getString("predicted"));

        } catch (JSONException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }
}
}

this line is the error in my code

tv1.setText(json.getString("predicted"));