The following historical data was compiled for the time (days) it takes to perform a task: 11, 18, 25, 30, 8, 42, 25, 30, 13, 21, 26, 35, 15, 23, 29, 36, 17, 25, 30, 21. Based on the given data, determine reasonable values for the PERT estimates a, m, and b for the task.