Wonder one thing How can I set a border of 1px around the last column

(defn main-panel []
  (let [text (re-frame/subscribe [::subs/read-value])]
  [:section.hero.is-fullheight
  [:div.hero-body.has-text-centered
    [:div.container
     [:div.box
     [:div.columns.is-flex.is-flex-direction-row
       [:div.column.is-two-fifths
         [:textarea.textarea {:rows 8, :on-change #(re-frame/dispatch [::events/update-text (-> % .-target .-value)])}]]
       [:div.column.is-one-fifths.is-flex.is-flex-direction-column
          [:button.button.is-primary.is-medium.flex-grow-1 {:on-click #(re-frame/dispatch[::events/read-text])} "Normal Text >>"]
          [:button.button.is-primary.is-medium.flex-grow-1.mt-3 {:on-click #(re-frame/dispatch[::events/uppercase-text])} "Uppercase Text >>"]
          [:button.button.is-primary.is-medium.flex-grow-1.mt-3 {:on-click #(re-frame/dispatch[::events/lowercase-text])} "Lowercase Text >>"]
          [:button.button.is-primary.is-medium.flex-grow-1.mt-3 {:on-click #(re-frame/dispatch[::events/reversed-text])} "reverse Text >>"]]
       [:div.column.is-two-fifths
          [:p @text]]]]]]]))

I use bulma