user: Question: Which class had a quantity made of 20?
Columns: ['Class', 'Wheel arrangement', 'Fleet number(s)', 'Manufacturer', 'Year made', 'Quantity made', 'Quantity preserved', 'Year(s) retired']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['2-8-2 — oOOOOo — Mikado', '2-8-2 — oOOOOo — Mikado', '2-8-2 — oOOOOo — Mikado', '2-8-2 — oOOOOo — Mikado', '2-8-2 — oOOOOo — Mikado', '2-8-2 — oOOOOo — Mikado', '2-8-2 — oOOOOo — Mikado', '2-8-2 — oOOOOo — Mikado']
SQL:

assistant: SELECT "Class" FROM "Table" WHERE "Quantity made" = '20';