Visualize exercise working times in exercise collection statstics

app/models/exercise_collection.rb

@@ -4,12 +4,16 @@ class ExerciseCollection < ActiveRecord::Base
   has_and_belongs_to_many :exercises
   belongs_to :user, polymorphic: true
 
-  def average_working_time
+  def exercise_working_times
     working_times = {}
     exercises.each do |exercise|
       working_times[exercise.id] = time_to_f exercise.average_working_time
     end
-    working_times.values.reduce(:+) / working_times.size
+    working_times
+  end
+
+  def average_working_time
+    exercise_working_times.values.reduce(:+) / exercises.size
   end
 
   def to_s