user: Question: What is the lowest image with a 20w Harrison, and less than 20 for Ashmolean?
Columns: ['Image', 'Smith', 'Ashmolean', 'Foster', 'Hahland', 'Dinsmoor', 'Hofkes-Brukker', 'Harrison', 'Cooper', 'BM/Corbett']
Types: ['real', 'text', 'real', 'real', 'real', 'text', 'text', 'text', 'text', 'text']
Sample row: [520.0, 'BM520', 21.0, 5.0, 9.0, '01N', '17W', '05E', '01N', '01N']
SQL:

assistant: SELECT MIN("Image") FROM "Table" WHERE "Harrison" = '20w' AND "Ashmolean" < 20.0;