To finalize the direction of a survey, four surveyors set up a theodolite at a station P and performed all the temporary adjustments. From the station P, each of the surveyors observed the bearing to a tower located at station Q with the same instrument without shifting it. The bearings observed by the surveyors are 30° 30' 00", 30° 29′ 40′′, 30° 30′ 20′′ and 30° 31′ 20′′. Assuming that each measurement is taken with equal precision, the most probable value of the bearing is