user: Question: Which graphics spec has a VRAM spec of 512MB?
Columns: ['Model', 'Processor', 'Memory', 'Storage', 'Graphics', 'VRAM', 'Display resolution', 'MSRP']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['MacBook Air 1.7GHz 11 in', '1.7GHz (Dual Core) Core i5', '4 GB 1600 MHZ', '64-512 GB SSD', 'Intel HD Graphics 4000', '256 MB Shared', '1366 × 768', '$999/ €999/ £814 / ₹67900']
SQL:

assistant: SELECT "Graphics" FROM "Table" WHERE "VRAM" = '512MB';