Instruction: Extract the value of the target attribute from the given product information and output it along with the corresponding source.

Input:
Product title: Lenovo IdeaPad Yoga 13 13.3-Inch Convertible 2 in 1 Touchscreen Ultrabook
Product description: The larger Yoga has a 13.3-inch IPS display (1600 x 900) and weighs 3.4 lbs. It is a mere .67 inches thick making it a true thin and light laptop that can also be used as a tablet.
Product feature: Intel Core i5-3317U CPU, 4GB DDR3 RAM, 128GB SSD, Windows 8 Standard 64-bit
Product price: $172.98
Product brand: Lenovo
Target attributes: Number of Cores
Answer: attribute: number of cores
value: None
source: None