Add a call to action button in the car campaigns english page

Tiny PR to add a primary cta to the car cost calculator on the car campaign page. Do we have a rails friendly url for the car cost tool?
the custom helper. link_to also hides things, but slightly less so. more importantly I think is codebase consistency, and using helpers like this isn't common in this codebase so should be avoided (as its a stylistic choice).