For Developer Intermediate > Lightning Components Basics > Attributes and Expressions challenge, even though it verified, but page is not displaying correctly.

It gave the following error when trying the run the page.

This page has an error. You might just need to refresh it.
Aura.loadComponent(): Failed to initialize application.
An internal server error has occurred
Error ID: 1877814438-103028 (-1501584897)

If I remove the required="true" from the aura:attribute it loads but it doesn't load any data.

Hi,
the challenge is as follows :

Create a camping component that contains a campingHeader and a campingList component.
1.The campingList component contains an ordered list of camping supplies that include Bug Spray, Bear Repellant, and Goat Food.
2.The campingHeader component contains an H1 heading style with a font size of 18 points and displays 'Camping List'.

so i made a lightening application named "camping.app" having code :

<aura:application >
    <br/><br/><br/>
    <c:campingHeader/>
    <c:campingList/>  
</aura:application>


where lightening component "campingHeader.cmp" having code :

<aura:component >
    <h1> Camping List </h1>
</aura:component>

for I have "campingHeader.css" having code :
.THIS {
}

h1.THIS {
    font-size: 18px;
}

and lightening component "campingList.cmp" having code :

<aura:component >
    <ol>
       <li>Bug Spray</li>
       <li>Bear Repellant</li>
       <li>Goat Food</li>      
    </ol>
</aura:component>

when i preview the application it is working nice; but when checking the challenge it says :
"Challenge Not yet complete... here's what's wrong: 
The 'camping' Lightning Component does not include either the campingHeader or campingList component."

please help me know where I m doing wrong. Thanx waiting for your reply