extjs 3.3 grid grouping and sum - extjs

Question

I want to write the sums of some data under grouping and grid. I am sharing my codes, I will be glad if you help. Thank you.
var store = new Ext.data.JsonStore({
url: 'ajaxQueryData?_qid=4146',
root: 'data',
totalProperty: 'browseInfo.totalCount',
remoteSort: true,
id: 'sira_no',
sortInfo: {
field: 'sira_no',
direction: 'ASC'
},
fields: [
{
name: "sira_no",
type: "int"
},
{
name: "branch_id_qw_"
},
{
name: "firma"
},
{
name: "sevk_adres"
},
{
name: "malzeme"
},
{
name: "group_id_qw_"
},
{
name: "kategori_id_qw_"
},
{
name: "alt_kategori_id_qw_"
},
{
name: "vade"
},
{
name: "birim_tip_qw_"
},
{
name: "miktar"
},
{
name: "kg"
},
{
name: "birim_fiyat"
},
{
name: "para_birim_qw_"
},
{
name: "net_tutar"
},
{
name: "irsaliye_dt"
},
{
name: "irsaliye_no"
},
{
name: "fatura_dt"
},
{
name: "fatura_no"
},
{
name: "sehir_id_qw_"
},
{
name: "ilce_id_qw_"
},
{
name: "satis_sorumlusu_id_qw_"
}
],
pageSize: 50,
autoLoad: {
params: {
startRow: 0,
fetchCount: 50
}
}
// proxy: new Ext.data.HttpProxy({
// })
});
var grid = new Ext.grid.GridPanel({
store: store,
columns: [{
id: 'sira_no',
header: 'Sıra No',
width: 50,
sortable: true,
dataIndex: 'sira_no'
},
{
header: 'Şube',
width: 150,
sortable: true,
dataIndex: 'branch_id_qw_'
},
{
header: 'Firma',
width: 250,
sortable: true,
dataIndex: 'firma'
},
{
header: 'Sevk Adresi',
width: 150,
sortable: true,
hidden: true,
dataIndex: 'sevk_adres'
},
{
header: 'Malzeme Adı',
width: 200,
sortable: true,
hidden: true,
dataIndex: 'malzeme'
},
{
header: 'Grup',
width: 100,
sortable: true,
dataIndex: 'group_id_qw_'
},
{
header: 'Kategori',
width: 100,
sortable: true,
dataIndex: 'kategori_id_qw_'
},
{
header: 'Alt Kategori',
width: 100,
sortable: true,
dataIndex: 'alt_kategori_id_qw_'
},
{
header: 'Vade (gün)',
width: 80,
sortable: true,
dataIndex: 'vade'
},
{
header: 'Birim',
width: 50,
sortable: true,
hidden: true,
dataIndex: 'birim_tip_qw_'
},
{
header: 'Miktar',
width: 80,
sortable: true,
hidden: true,
dataIndex: 'miktar'
},
{
header: 'Kg',
width: 80,
sortable: true,
dataIndex: 'kg'
},
{
header: 'Birim Fiyat',
width: 80,
sortable: true,
dataIndex: 'birim_fiyat'
},
{
header: 'Para Birimi',
width: 50,
sortable: true,
dataIndex: 'para_birim_qw_'
},
{
header: 'Net Tutar',
width: 80,
sortable: true,
dataIndex: 'net_tutar'
},
{
header: 'İrsaliye Tarihi',
width: 100,
sortable: true,
hidden: true,
dataIndex: 'irsaliye_dt'
},
{
header: 'İrsaliye No',
width: 100,
sortable: true,
hidden: true,
dataIndex: 'irsaliye_no'
},
{
header: 'Fatura Tarihi',
width: 100,
sortable: true,
hidden: true,
dataIndex: 'fatura_dt'
},
{
header: 'Fatura No',
width: 100,
sortable: true,
hidden: true,
dataIndex: 'fatura_no'
},
{
header: 'Şehir',
width: 120,
sortable: true,
dataIndex: 'sehir_id_qw_'
},
{
header: 'İlçe',
width: 120,
sortable: true,
dataIndex: 'ilce_id_qw_'
},
{
header: 'Satış Sorumlusu',
width: 200,
sortable: true,
dataIndex: 'satis_sorumlusu_id_qw_'
}
],
viewConfig: {
forcefit: true
},
//resizable: true,
width: function() {
$("#aciklama").width();
$(document).ready(function() {
$(".slide-left").click(function() {
Width: $("#aciklama").width();
})
$(".slide-right").click(function() {
Width: $("#aciklama").width() - 334;
})
})
},
height: $("#aciklama").height(),
frame: true,
tbar: new Ext.PagingToolbar({
pageSize: 50,
store: store,
displayInfo: true
})
});
grid.render('aciklama');