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: Zenith Z42PX2D 42-Inch Flat Panel ED-Ready Plasma TV
Product description: Groundbreaking display technology delivers superior image clarity, color and brightness in a large-format television that is less than 4" thick. Includes built-in EDTV Tuner, ATSC/NTSC/QAM Tuner, speakers. Stand included in Box. DCR(CableCARD), PSIP Guide, 5000:1 Contrast Ratio, HDMI, 852x480P resolution.
Product feature: ATSC/NTSC/QAM Clear Tuners, Digital Cable Ready (CableCARD); HDMI with HDCP, 5000:1 Contrast Ratio, 1000 cd/m(2) Brightness, Speakers Built-in, Stand Incl.. Connectivity technology: 1 HDMI, VGA
Product brand: Zenith
Target attributes: Refresh Rate
Answer: attribute: refresh rate
value: None
source: None