Where to put img height and width?

The images in my single classified featured image are too big. I want them smaller. Something with +- 500x500px.

I’m sure that I have the right HTML-code:
elseif ( $default ) {
echo ‘<img class=”classified_featured_image” src=”‘ . esc_attr( $default ) . ‘” />’;
} else {
echo ‘<img class=”classified_featured_image” src=”‘ . esc_attr( apply_filters( ‘classified_manager_default_classified_featured_image’, WP_CLASSIFIED_MANAGER_PLUGIN_URL . ‘/assets/images/placeholder.png’ ) ) . ‘” />’;
}

Where can I put the height and width in the code above?