What is the last name and position of the student that bought pizza on 09/10/2019?
bought pizza on 09/10/2019 refers to expense_description = 'Pizza' where expense_date = '2019-09-10'
SELECT T1.last_name, T1.position FROM member AS T1 INNER JOIN expense AS T2 ON T1.member_id = T2.link_to_member WHERE T2.expense_date = '2019-09-10' AND T2.expense_description = 'Pizza'