Provide the number of staff at the University of Auckland in 2015.
University of Auckland refers to university_name = 'University of Auckland'; in 2015 refers to year = 2015; number of staff refers to DIVIDE(num_students, student_staff_ratio)
SELECT CAST(SUM(T1.num_students) AS REAL) / SUM(T1.student_staff_ratio) FROM university_year AS T1 INNER JOIN university AS T2 ON T1.university_id = T2.id WHERE T2.university_name = 'University of Auckland' AND T1.year = 2015