Get row count from testimonial category

Hello,

I am trying to display the number of testimonials assigned to certain categories.

My code:

global $wpdb;
$biz_end = $wpdb->get_var( "SELECT object_id FROM $wpdb->mb_term_relationships WHERE term_taxonomy_id = '40'" );

Business Endorsement (<?php echo count($biz_end); ?>)

I’m not getting any results using the above.

http://wordpress.org/extend/plugins/gc-testimonials/