function calculatePrice()
{     
    var total = 0.0;
    
    jQuery(".SizeOption").each(function(){
        if( ! this.checked) return;
        var size_id = this.value;
        if( ! size_id ) return;
                          
        var price = size_prices[size_id];
        
        total += price;
    });   
    
    return total;    
}

function updatePrice()
{
    var price = calculatePrice();
    $("#total-price").html( "$" + price.toFixed(2) );
}