How to resize header in Twentyeleven theme using Custom Headers?

Hi,
I have tried to follow the instructions in http://codex.wordpress.org/Custom_Headers to customise the height of the header image using a child theme. Accordingly, I created a functions.php file in the child theme folder with the following code:

‘<?php
$args = array(
‘width’ => 980,
‘height’ => 50,
‘default-image’ => get_template_directory_uri() . ‘/images/header.jpg’,
‘uploads’ => true,
);
add_theme_support( ‘custom-header’, $args );’

However, the header image remains as its default height. I guess I am missing something.

Do I also have to update the header.php file? If so, can I do it in the child theme and what code should I put into it?

Any help is appreciated. Thanks.

[ Please do not bump, it’s not permitted here. ]