After researching tumors of a particular type, a doctor learns that out of 10,000 such tumors examined, 1500 are malignant and 8500 are benign. A diagnostic test is available which gives the correct diagnosis 80% of the time (whether the tumor is malignant or not). The doctor has discovered the same type of tumor in a new patient and decides to begin diagnosis by using the diagnostic test. If the test says that the tumor is malignant, what is the probability that the patient actually does have a malignant tumor?