user: Question: Name of 900 north michigan, and a Year smaller than 1989 involves what lowest floors?
Columns: ['Name', 'Street Address', 'Height feet / meters', 'Floors', 'Year']
Types: ['text', 'text', 'text', 'real', 'real']
Sample row: ['Trump International Hotel & Tower', '401 N. Wabash Avenue', '1,170 / 356.6', 92.0, 2008.0]
SQL:

assistant: SELECT MIN("Floors") FROM "Table" WHERE "Name" = '900 north michigan' AND "Year" < 1989.0;