Get data from 2 tables

Hi, i have 4 tables: questions, answers, users, and inquiries
(relationship)

  def index
    question_id = params[:id].to_i
    question = Question.find(question_id)
    @answers = question.answers

    respond_to do |format|
      format.ext_json { render :json => @answers.to_ext_json(:class =>
Answer) }
    end
  end

I have several scaffold in extjs, when I click on row, i get answers on
question that i just selected, COOL. But i need paste in this info email
of people (emails stores in users table). Now i have this:

id | answer |

  1 | lala
  2 | lalala2

but i need this:

id | answer | email

  1 | lala | alal@sa.com
  2 | lal2 | asasa@was.net