user: Question: What was the quantity preserved for quantity made of 15?
Columns: ['Class', 'Wheel arrangement', 'Manufacturer', 'Year made', 'Quantity made', 'Quantity preserved', 'Year(s) withdrawn']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Joseph Hamilton Beattie (1850–1871)', 'Joseph Hamilton Beattie (1850–1871)', 'Joseph Hamilton Beattie (1850–1871)', 'Joseph Hamilton Beattie (1850–1871)', 'Joseph Hamilton Beattie (1850–1871)', 'Joseph Hamilton Beattie (1850–1871)', 'Joseph Hamilton Beattie (1850–1871)']
SQL:

assistant: SELECT "Quantity preserved" FROM "Table" WHERE "Quantity made" = '15';