a technician connects a dmm with a min/max/avg function to the output of an oxygen sensor. the engine is run at 2000 rpm for several minutes. during the test, the voltage toggles rapidly between 150 and 900 millivolts. at the end of the test, the max voltage was .967 v, the min voltage was .087 v, and the avg voltage was .783 v. technician a says the sensor is sticking lean. technician b says there could be a vacuum leak that caused the sensor voltage to have a higher than normal average. who is correct?