javascript - Knockout computed observable not working -

i using knockout computed observable multiply 2 other observables. unfortunately, computed observable not seem outputting value.

var boyle1 = { volume1_text: ko.observable(parseint(2)), volume1_select: ko.observable(parseint(2)) }; boyle1.volume = ko.computed(function () {     return this.volume1_text() * this.volume1_select(); }, boyle1); ko.applybindings(boyle1); 

both other observables work perfectly, , binded elements on page. doing wrong?

it has html binding computed. indicated in fact, typo in markup.

markup

<input data-bind="value: volume1_text" /> <input data-bind="value: volume1_select" /> <br /><br />     <span data-bind="text: volume"></span> 

model

var boyle1 = {    volume1_text: ko.observable(parseint(2)),    volume1_select: ko.observable(parseint(2)) };  boyle1.volume = ko.computed(function () {     return this.volume1_text() * this.volume1_select(); }, boyle1);  ko.applybindings(boyle1); 

here working example of model , problem

http://jsfiddle.net/ybr2m/1