JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://ajax.aspnetcdn.com/ajax/knockout/knockout-3.0.0.js"></script>
<script src="https://raw.github.com/SteveSanderson/knockout.mapping/master/build/output/knockout.mapping-latest.debug.js"></script>
<!-- ko foreach: Foo.Bar.Collection -->
<span data-bind="text: Price"></span>
*
<span data-bind="text: $root.Count"></span>
=
<span data-bind="text: Total"></span>
<br />
<!-- /ko -->

JavaScript

var mapping = {
    'Collection': {
        create: function(options) {
            var model = ko.mapping.fromJS(options.data);
            model.Total = ko.computed(function() {
                var result = this.Price() * 10;
                //var result = this.Price() * viewModel.Count(); // :(
                return result;
            }, model);

            return model;
        }
    }
};

var json = {
    Count: 10,
    Foo: {
        Bar: {
            Collection: [
                { Price: 5 },
                { Price: 1 },
                { Price: 2 },
                { Price: 12 }
            ]
        }
    }
};

var viewModel = ko.mapping.fromJS(json, mapping);
ko.applyBindings(viewModel);