Resize content inserted after paragraph post

Hello, I inserted this code to put adsense ad code, and it works well,

//Publicidad tras un párrafo concreto
add_filter( 'the_content', 'publicidad_tras_parrafo' );
function publicidad_tras_parrafo( $content ) {
        if( !is_single() )
            return $content;

            $paragraphAfter = 3; //Este es el número del párrafo tras el que irá la publicidad
            $content = explode ( "</p>", $content );
            $new_content = '';
                for ( $i = 0; $i < count ( $content ); $i ++ ) {
                    if ( $i == $paragraphAfter ) {
                    $new_content .= '<div style="width: 600px; height: 100px; padding: 5px 5px 5px 0; margin-right: 0;">';
                    $new_content .= 'adsense code';
                    $new_content .= '</div>';
                    }
            $new_content .= $content[$i] . "</p>";
            }
            return $new_content;
    }

but I would put it adaptable to the size of the screen, that is not always stick with these features:

$new_content .= '<div style="width: 600px; height: 100px; padding: 5px 5px 5px 0; margin-right: 0;">';

What values should be given for the size of the content depending on the size of the screen? thanks