jQuery Calculations not working out

I'm using the jQuery Calculator plugin (http://www.pengoworks.com/workshop/jquery/calculation/calculation.plugin.htm) and have stumbled across a small problem w开发者_运维问答hen calculating the cost of cupcakes.

I need £19 for 1-12 products, £37 for 13-24 products, or £1.45 each for 25+ products but can't work out how to change the sum to show this.

Can anyone please help?

My code so far...

var bIsFirebugReady = (!!window.console && !!window.console.log);

$(document).ready(
    function (){
        // update the plug-in version
        $("#idPluginVersion").text($.Calculation.version););


        // bind the recalc function to the quantity fields
        $("input[name^=qty_item_]").bind("keyup", recalc);
        // run the calculation function now
        recalc();

        // automatically update the "#totalSum" field every time
        // the values are changes via the keyup event
        $("input[name^=sum]").sum("keyup", "#totalSum");

        // automatically update the "#totalAvg" field every time
        // the values are changes via the keyup event
        $("input[name^=avg]").avg({
            bind:"keyup"
            , selector: "#totalAvg"
            // if an invalid character is found, change the background color
            , onParseError: function(){
                this.css("backgroundColor", "#cc0000")
            }
            // if the error has been cleared, reset the bgcolor
            , onParseClear: function (){
                this.css("backgroundColor", "");
            }
        });

        // automatically update the "#minNumber" field every time
        // the values are changes via the keyup event
        $("input[name^=min]").min("keyup", "#numberMin");

        // automatically update the "#minNumber" field every time
        // the values are changes via the keyup event
        $("input[name^=max]").max("keyup", {
            selector: "#numberMax"
            , oncalc: function (value, options){
                // you can use this to format the value
                $(options.selector).val(value);
            }
        });

        // this calculates the sum for some text nodes
        $("#idTotalTextSum").click(
            function (){
                // get the sum of the elements
                var sum = $(".textSum").sum();

                // update the total
                $("#totalTextSum").text("$" + sum.toString());
            }
        );

        // this calculates the average for some text nodes
        $("#idTotalTextAvg").click(
            function (){
                // get the average of the elements
                var avg = $(".textAvg").avg();

                // update the total
                $("#totalTextAvg").text(avg.toString());
            }
        );
    }
);

function recalc(){


    $("[id^=total_item]").calc(
        // the equation to use for the calculation

        if(qty > 24){

            "qty * price",
        // define the variables used in the equation, these can be a jQuery object
        {
            qty: $("input[name^=qty_item_]"),
            price: $("[id^=price_item_]"),

        },

        }else{

            "qty = fee",
        // define the variables used in the equation, these can be a jQuery object
        {
            qty: $("input[name^=qty_item_]"),
            fee: ($("input[name^=qty_item_]").val() < 13) ? 19 : 37 ,

        },

        }




        // define the formatting callback, the results of the calculation are passed to this function
        function (s){
            // return the number as a dollar amount
            return "£" + s.toFixed(2);
        },
        // define the finish callback, this runs after the calculation has been complete
        function ($this){
            // sum the total of the $("[id^=total_item]") selector
            var sum = $this.sum();

            $("#grandTotal").text(
                // round the results to 2 digits
                "£" + sum.toFixed(2)
            );
        }
    );
}

I have even tried...

    function recalc(){

        // define the variables used in the equation, these can be a jQuery object
        var qty = $("input[name^=qty_item_]");
        var price = $("[id^=price_item_]");
        var fee = ($("input[name^=qty_item_]").val() < 13) ? 19 : 37;

    $("[id^=total_item]").calc(
        // the equation to use for the calculation

        if(qty > 24){

            "qty * price",


        }else{

            "qty = fee",

        }

---

I'm interested in calculation plugin for jQuery myself so I managed to fix your source as an exercise. Check if it works the way you like and read the code carefully.

Link: http://jsfiddle.net/Q3Nwd/3/