user: Question: If the position in table is 10th, and the manner of departure was Resigned, what was the date of vacancy?
Columns: ['Team', 'Outgoing head coach', 'Manner of departure', 'Date of vacancy', 'Position in table', 'Incoming head coach', 'Date of appointment']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['União de Leiria', 'Lito Vidigal', 'Sacked', '7 July 2010', 'Off-season', 'Pedro Caixinha', '10 July 2010']
SQL:

assistant: SELECT "Date of vacancy" FROM "Table" WHERE "Manner of departure" = 'Resigned' AND "Position in table" = '10th';