Trouble with Associations

So I'm adding a very basic forum to my site and am having some trouble calling the right associations (I know it's a newbie mistake, but can't seem to figure out where my thinking is wrong.)

I have forums -> topics -> posts.

Forum: has_many topics
Topics: has_many posts, belongs_to forum, belongs_to user
Posts: belongs_to topic, belongs_to user

Now, in the forum/show page, I want to list all the topics for that forum (and that is working with the following code) <table class="table table-striped"> <tr> <th>Topic</th> <th>Last Reply</th> <th>Number of Replies</th> </tr> <% @forum.topics.each do |topic| %> <tr> <td> <h4><%= link_to topic.title, forum_topic_path(@forum, topic.id) %></h4><br/> Started by: <%= topic.user.full_name %> </td> <td></td> <td> <%= topic.posts.count %> </td> </tr> <% end %> </table>

And here's the show action in the controller:

def show
@forum = Forum.find(params[:id])
@topic = @forum.topics
add_breadcrumb @forum.title, forum_path(@forum)

respond_to do |format|
  format.html # show.html.erb
  format.json { render json: @forum }
end
  end

Now, I have the count working (in that it's counting the number of posts correctly for each topic), but I want to call the last post for each topic to display the time and the user who posted last. This is where I am running into difficulties.

Any ideas? I'm able to get the last post by calling:

topic.posts.last

But am unsure how to get out the user and created_at column.

Any help would be great! Thanks!