Use the graph on Fusion p. 521 (or online Fusion textbook) to complete this question. Pertussis, or whooping cough, is a highly contagious disease that affects the respiratory system. The vaccine for the disease is only effective for a few years. The bar graph below shows the number of cases of whooping cough that occurred in Sydney, Australia, during the first half of 2005. Using the graph on Fusion p. 521 (or online Fusion textbook), what percentage of cases occurred in people younger than 30 years old?