     result = Langtrainer.LangtrainerApp.apiEndpoint + '/verify_answer'
     result += @baseParams()
     result += '&answer=' + answer
+    result += '&difficulty_index=' + @difficultyIndex(answer)
 
   nextStepUrl: ->
     result = Langtrainer.LangtrainerApp.apiEndpoint + '/next_step'

class Langtrainer.LangtrainerApp.Models.Step extends Backbone.Model
  baseParams: ->
    result = '?token=' + Langtrainer.LangtrainerApp.currentUser.readAttribute('token')
    result += '&unit=' + Langtrainer.LangtrainerApp.world.get('unit').get('id')

    $.ajax
      url: @showRightAnswerUrl()
      dataType: 'json'

    @stepsHelped += 1
