Filter not working

Trying to add a filter to increase shipping fee’s by 3%. Added the filter code below to start with in my custom css section and it gave me an error. Any suggestions?

add_filter(‘hitstacks_fedex_shipping_cost_conversion’,’fedex_shipping_cost_conversion’,10,1);
function fedex_shipping_cost_conversion($ship_cost){
return $ship_cost+1000;
}

The page I need help with: [log in to see the link]