Cover image thumb

I would like to have a thumb for my cover image with a specific format 400x300.
How can I do this?


<div class="row">
					<?php foreach(page('news')->children()->visible()->limit(3)->flip() as $article): ?>
                    <div class="col col-lg-4">
							<div class="blog-grids">
								<div class="grid">
									<div class="entry-header">
										<div class="entry-media">
											<?php snippet('coverimage', $article) ?>
										<div class="entry-meta">
												<li><i class="fa fa-calendar"></i> <a href="<?= $article->url() ?>"><?= $article->date('F jS, Y') ?></a></li>
									<div class="entry-body">
										<div class="entry-body">
                                    <h3><a href="<?= $article->url() ?>"><?= $article->title()->html() ?></a></h3>
                                    <p><?= $article->text()->kirbytext()->excerpt(50, 'words') ?></p>
                                    <a href="<?= $article->url() ?>" class="read-more"><?php echo l::get('btn-read-more') ?> <i class="fa fa-angle-right"></i></a>

Snippet cover image

<?php if($image = $item->coverimage()->toFile()): ?>
	<img src="<?= $image->url() ?>" alt="" />
<?php endif ?>

It’s all in the docs: