Instruction: Using the product's title, description, features, price, and brand, identify and retrieve the values associated with a specified set of target attributes. Output the extracted values along with their respective sources (e.g., title or feature) indicating where each value was found.

Input:
Product title: Apple MacBook Air Core i7 1.8GHz 11"-4GB RAM-128GB SSD-Lion-(2011)
Product description: Apple MacBook Air Core i7-2677M Dual-Core 1.8GHz 4GB 256GB SSD 11.6" LED Notebook AirPort OS X w/Cam (Mid 2011) (Refurbished)
Product feature: Apple MacBook Air Core i7-2677M Dual-Core 1.8GHz 4GB 256GB SSD 11.6" LED NotebookOS X w/Cam(2011)-Refurbished, 90 days warranty for refurbished products - 1 year for new products, Fast shipping
Product brand: Apple
Target attributes: Weight
Answer: attribute: weight
value: None
source: None