Cannot read property 'extend' of undefined

While running this code i got an error that "cannot read property extend of undefined"

 App.Produt=DS.Model.extend({
    name:DS.attr(),
    description:DS.attr(),
    price:DS.attr()
 });
 App.Store=DS.Store.extend({

adapter:'DS.FixtureAdapter' 
});

 App.ProductAdapter=DS.FixtureAdapter.extend();
 App.Product.FIXTURES=[
    {
        id:1,
        name:'playstation 3',
        description:'something',
        price:200
    }
 ];