How to get the information from only one category and display it

The following code gets all the respective information from all the categories, but kindly help me to get information from only one category, (ie:- category name is Promoted Coupon, ID is 12. I cant figure out how to code it.

THANX IN ADVANCE

<ul class="rr slides">
<?php
	$args = array(	);
	$args['post_type'] = 'coupons';
	$args['posts_per_page'] = 8;
	$query = new WP_Query($args);
	while($query->have_posts() ) : $query->the_post();
	$discount = get_post_meta($post->ID, '_single_discount', true);
	$date = get_post_meta($post->ID, '_single_date', true);
	$code = get_post_meta($post->ID, '_single_code', true);
	$url = get_post_meta($post->ID, '_single_url', true);
	$thumbs = array();
	$categories = get_the_category();
	$thumb = wp_get_attachment_url( get_post_thumbnail_id($post->ID) );
		if($categories) {
		foreach($categories as $category) {
		$image = get_option('taxonomy_' . $category->term_id);
			if($image) {
			if($thumb == '') {
				$thumb = $image['custom_term_meta'];
			        }
				$category_id = $category->term_id;
				}
			}
		}
	$daysleft = round( ($date-time()) / 24 / 60 / 60);
	?>
	<li>
	<div class="wrapper-3 item-thumb">
		<div class="top">
		<figure>
		<a href="<?php echo get_category_link( $category_id );?>">
		<img src="<?php echo aq_resize($thumb, 200, 140, true); ?>"     alt="<?php the_title();?>">
		</a>
		</figure>
	<h2 class="alt"><a href="<?php the_permalink();?>"><?php truncate_title(15);?></a></h2>
	</div>
	<div class="bottom">
	<?php if($discount != '') { ?>
	<p class="value secondary"><?php echo $discount;?></p>
		<?php } ?>
		<h6>
	<?php
										if($date == '')
	_e('VALID', 'Couponize');
	else if($daysleft <= 0) 								_e('EXPIRED', 'Couponize');
	else echo sprintf( _n('%d day left.', '%d days left.', $daysleft, 'Couponize'), $daysleft ); ?>
		</h6>
	</div>
</div>
</li>
<?php endwhile; wp_reset_postdata();?>
</ul>