Instruction: Parse the product information to locate the target attribute, and then provide the extracted value of the target attribute and its source in the output, specifying None if the attribute is not present.

Input:
Product title: ZOTAC NVIDIA GeForce GTX 660 2GB GDDR5 2DVI/HDMI/DisplayPort PCI-Express Video Card ZT-60901-10M
Product description: ZOTAC NVIDIA GeForce GTX 660 2GB GDDR5 2DVI/HDMI/DisplayPort PCI-Express Video Card
Product feature: Chipset: NVIDIA GeForce GTX 660, Video Memory: 2GB GDDR5, Memory Interface: 192-bit, Max Resolution: 2560 x 1600, Connectors: DVI-I, DVI-D, HDMI, DisplayPort, Thermal: Fansink (Dual Fans)
Product brand: ZOTAC
Target attributes: Length
Answer: attribute: length
value: None
source: None