Iterating through related models in Ember.js

I have the following models, which have basic associations, as you can see below:

App.PricingSummary = DS.Model.extend({
    startDate: DS.attr(),
    endDate: DS.attr(),
    days: DS.hasMany('day', {async: true})
});

App.Day = DS.Model.extend({
    date: DS.attr(),
    rate: DS.belongsTo('rate', {async: true})
});

App.Rate = DS.Model.extend({
    price: DS.attr()
});

The concept here is that a PricingSummary contains a set of Days, each of which has a Rate which is basically the price for that day. Rate needs to be its own model as there is supposed to be a finite set of values from which to assign to a day.

What I'm trying to do is in my controller, which has a context of a PricingSummary model, loop through the Days in the PricingSummary and find the lowest Rate for that period.

Here's my attempt at doing so:

barRange: function(){
    var lowBar;

    this.get('days').then(function(days){

        days.forEach(function(day){

            day.get('rate').then(function(rate){
                rateValue = rate.get('price')

                if(typeof lowBar === 'undefined' || rateValue < lowBar){
                    lowBar = rateValue;
                }
            });

        });

        console.log( 'lowBar is ' + lowBar )
    });

}.property('days')

I think this is really only half-baked... but it shows you the way I'm approaching it, which may or may not be completely wrong. Is there a better way to do this? If not, what are the last pieces that I'm missing here?