Table: manager_changes
Columns: team
outgoing_manager
manner_of_departure
date_of_vacancy
replaced_by
date_of_appointment

Question: How many have been replaced where the appointment date is 10 December 2007 and the manner of departure is quit?
SQL: SELECT COUNT("replaced_by") FROM manager_changes WHERE "date_of_appointment" = '10 December 2007' AND "manner_of_departure" = 'Quit'

Question: What is the date of vacancy for 10 december 2007 when quit?
SQL: SELECT "date_of_vacancy" FROM manager_changes WHERE "date_of_appointment" = '10 December 2007' AND "manner_of_departure" = 'Quit'

Question: How many manners of departure did peter voets have?
SQL: SELECT COUNT("manner_of_departure") FROM manager_changes WHERE "outgoing_manager" = 'Peter Voets'