respond_with and ajax

Suppose I have this controller:

class SalesController < ApplicationController   respond_to ???

  def get_price     @price = Product.find(params[:product_id]).price     respond_with ???   end

end

1) What do I specify for respond_to() so that get_price() will accept ajax requests?

2) What do I specify for respond_with() if all I want to do is return @price?