I am doing the Handling Events with Client-Side controllers for the Lightning components study. I created the following:
the javascript modules : PhoneNumberInput and PhoneNumberOutput
The phone number input file contains
<aura:component >
    <aura:registerEvent name="PhoneNumEvent" type="c:PhoneNumEvent"/>
    <ui:inputPhone aura:id="phone" label="phone" />
    <ui:button label="Show Phone" press="{!c.postphone}" />
</aura:component>

The event fle PhoneNumberEvent.evt  - I believe that this is the file name I was supposed to use.
and the application file PhoneNumber.app  - Not sure what file name to use.
 
Everything runs fine, the problem is when I check the results I get the error:
Challenge not yet complete... here's what's wrong:
The 'PhoneNumberEvent' event is not of type 'APPLICATION'.