4. Diseases D1, D2, and D3 cause symptom A with probabilities 0.5, 0.7, and 0.8, respectively. If 5% of a population have disease D1, 2% have disease D2, and 3.5% have disease D3, what percent of the population have symptom A? Assume that the only possible causes of symptom A are D1, D2, and D3 and that no one carries more than one of these three diseases.