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: Calvin Klein Men's Underwear Cotton Stretch 3 Pack Briefs
Product description: Cotton stretch briefs multipack, classic fit with cotton stretch fabric for comfort and shape retention and a soft, breathable, durable cotton stretch blend waistband with iconic Calvin Klein logo. 3-pack.
Product feature: 95% Cotton, 5% Elastane, Imported, Pull On closure, Machine Wash, Cotton stretch underwear briefs multipack featuring comfortable elastic Calvin Klein logo waistband, Soft and breathable stretch cotton blend, Packs are available in assorted colors, Stretch fabrication for comfort and shape retention, Durable, everyday briefs pack, Package Dimensions: 1 x 1 x 1 inches, Shipping Weight: 1 pounds, ASIN: B00KLV6K6G, Item model number: NU2661, Date first listed on Amazon: October 1, 2015, Domestic Shipping: Item can be shipped within U.S., International Shipping: This item is not eligible for international shipping. Learn More, Average Customer Review: 4.6 out of 5 stars 7 customer reviews
Target attributes: Silhouette
Answer: attribute: silhouette
value: briefs
source: product title
attribute: silhouette
value: briefs
source: product description
attribute: silhouette
value: briefs
source: product feature