Coupon css question

After a frustrating hour or so digging and tinkering with css I can’t figure something out. In the coupon page I want to have one of clickable links in bold and underlined, to make it more obvious.

I found the section in css.core.styles.css, but if I change the link which is under span7 to font-weight:bold everything changes into bold and the link is still not obvious. Same with underline.

How can I change just the clickable link, which says CLICK HERE TO USE DEAL in bold and underlined, and not everything else? I attached a screenshot, where you can see all text is bold now.

Or check it here: https://shoppingdeals4u.com/coupon/thorntons-discount-code/

Thanks
Jasper

Thanks in advance