user: Question: What is the total number of t (µm), when Technology is u c-si?
Columns: ['Technology', 'η (%)', 'V OC (V)', 'I SC (A)', 'W/m²', 't (µm)']
Types: ['text', 'real', 'text', 'text', 'text', 'real']
Sample row: ['u c-Si', 24.7, '0.5', '0.8', '63', 100.0]
SQL:

assistant: SELECT SUM("t (µm)") FROM "Table" WHERE "Technology" = 'u c-si';