Grid with computed column

HTML

<link rel="stylesheet" href="http://cdn.kendostatic.com/2013.2.716/styles/kendo.common.min.css">
<link rel="stylesheet" href="http://cdn.kendostatic.com/2013.2.716/styles/kendo.default.min.css">
<script src="http://cdn.kendostatic.com/2013.2.716/js/jquery.min.js"></script>
<script src="http://cdn.kendostatic.com/2013.2.716/js/kendo.all.min.js"></script>
<script src="http://demos.kendoui.com/content/shared/js/people.js"></script>
<div id="grid"></div>

CSS

#grid {
    width : 490px;
}

JavaScript

var ds = {
    data    : [
        { Id: 1, ItemName: "Galaxy", Price: "25000", Qty: 2, Total: 50000 },
        { Id: 1, ItemName: "Lumia", Price: "18000", Qty: 1, Total: 18000 },
        { Id: 1, ItemName: "Experia", Price: "10000", Qty: 3, Total: 30000 } 
    ],
    pageSize: 10,
    schema  : {
        model: {
            id : "Id",
            fields: {
                Id       : { type: 'number' },
                ItemName : { type: 'string' },
                Price    : { type: 'number' },
                Qty      : { type: 'number' },
                Total    : { type: 'number' }
            }
        }
    }
};

var grid = $("#grid").kendoGrid({
    dataSource: ds,
    editable  : "incell",
    pageable  : false,
    columns   :
    [
        { field: "ItemName", title: "Item Name" },
        { field: "Price", title: "Price" },
        { field: "Qty", title: "Qty" },
        { field: "Total", title: "Total" }
    ],
    save : function (e) {
        if (e.values.Qty || e.values.Price) {
            var qty = e.values.Qty || e.model.Qty;
            var price = e.values.Price || e.model.Price;
            e.model.set("Total", price * qty);
        }
    }
}).data("kendoGrid");