Как суммировать столбцы в таблице данных jquery

Как суммировать значения столбцов в таблице данных?

var sTable = $('.datatable').dataTable({
    "bJQueryUI": true,
    "sPaginationType": "full_numbers",
    "bScrollCollapse": true,
    "aaSorting": [[1, "desc"]],
    "bServerSide": true,
    "bProcessing": true,
    "sAjaxSource": CycleTimeReport,
    "aoColumns": [
        { "sName": "Course", "sClass": "ellipsis" },
        { "sName": "Cost", "sClass": "ellipsis" }
    ],
    "fnServerData": function (sSource, aoData, fnCallback) {
        var data = new Object();
        data.jsonAOData = JSON.stringify(aoData);
        dataToSend = data;

        $.ajax({
            contentType: "application/json; charset=utf-8",
            type: "POST",
            url: sSource,
            data: JSON.stringify(dataToSend),
            success: function (msg) {
                fnCallback(msg);
            },
            error: function (XMLHttpRequest, textStatus, errorThrown) {
                if (document.Invoice.hostname == "localhost") {
                    alert(XMLHttpRequest.status);
                    alert(XMLHttpRequest.responseText);
                }
            }
        });
    },
    "fnDrawCallback": function (aoData, oObj) {

    },
    "oLanguage": {
        "sSearch": "_INPUT_"
    },
    "fnInitComplete": function (oSettings, json) {
    },
    "bSortCellsTop": true
});