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: Lenovo ThinkCentre M900 10FH000MUS Desktop Computer - Intel Core i7 i7-6700 3.40 GHz
Product description: Thinkcentre M900, Intel Core i7-6700 3.40GHz, 8MB, Windows 7 professional 64 preinstalled through downgrade rights in Windows 10 Pro, 8.0GB, 1x1tb SATA III, NVIDIA 720, DVD recordable, x, Intel 8260, 3Yr OS intel del
Product feature: Thinkcentre M900, Design that delivers high availability, scalability, and for maximum flexibility and price/performance, Made in China
Product price: $669.00
Product brand: Lenovo
Target attributes: Number of Cores
Answer: attribute: number of cores
value: None
source: None