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: Asus ATI Radeon HD4670 1 GB DDR3 PCI Express 2.0 x16 HDCP Ready CrossFire Supported Video Card EAH4670/DI/1GD3/V2/A
Product description: ASUS EAH4670/DI/1GD3/A Radeon HD 4670 1GB 128-bit GDDR3 PCI Express 2.0 x16 HDCP Ready Video Card (DVI / /2nd VGA /HDMI /TV-out /HDTV Support) CrossFire Ready
Product feature: Native HDMI port build-in with low-profile Design, Radeon HD4670, Engine Clock: 750 MHz, 1G of DDR3 memory. Memory Clock: 1.6Ghz MHz. Memory Interface: 128bit, DVI / /2nd VGA /HDMI /TV-out /HDTV Support
Product brand: Asus
Target attributes: Manufacturer
Answer: attribute: manufacturer
value: asus
source: product description
attribute: manufacturer
value: asus
source: product title
attribute: manufacturer
value: asus
source: product brand