Suppose that we are interested in studying patients with systemic cancer who subsequently develop a brain metastasis; our ultimate goal is to prolong their lives by controlling the disease. A sample of 23 such patients, all of whom were treated with radiotherapy, were followed from the first day of their treatment until recurrence of the original tumor. Recurrence is defined as the reappearance of a metastasis in exactly the same site, or in the case of patients whose tumor never completely disappeared, enlargement of the original lesion. Times to recurrence (in weeks) for the 23 patients were: 2, 2, 2, 3, 4, 5, 5, 6, 7, 8, 9, 10, 14, 14, 18, 19, 20, 22, 22, 31, 33, 39, and 195. Calculate and graph the Kaplan-Meier curve.