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

If the number of sides resulting in a closed traverse is increased from three to four, the sum of the interior angles increases by

A surveyor observes a zenith angle of 93° 00′ 00″ during a theodolite survey. The corresponding vertical angle is

Among the following statements relating the fundamental lines of a transit theodolite, which one is CORRECT?