Database: food_inspection_2
Question: After Azha Restaurant Inc. passed the inspection on 2010/1/21, when was the follow-up inspection done?
SQL: SELECT T1.followup_to FROM inspection AS T1 INNER JOIN establishment AS T2 ON T1.license_no = T2.license_no WHERE T2.dba_name = 'Azha Restaurant Inc.' AND T1.results = 'Pass' AND T1.inspection_date = '2010-01-21'