<image>(2009 Autumn • Pingdu City's school-level final) During a donation event, 50 students from Class 3 of Grade 7 each contributed their own pocket money. Some students donated 5 yuan, 10 yuan, 20 yuan, while others donated 50 yuan and 100 yuan. The following statistical graph shows the proportion of students who donated different amounts. What is the average donation per student in this class? ____ yuan.