Instruction: First, identify the target attributes from the provided list. Then, scan the product title, description, feature, and brand to extract the values associated with each target attribute. Finally, create a list of dictionaries, each containing the extracted attribute, its corresponding value, and the source where it was found.

Input:
Product title: Silvertone SS15 WHT Solid-Body Electric Guitar, Gloss White
Product description: Double cut-a-way electric guitar with a vintage tremolo and a 1 year warranty
Product feature: 3 single coil pickups, Low profile maple neck for easy playing, 3 way pickup switch, 3 single coil pickups, Low profile maple neck for easy playing
Product price: $26.24
Product brand: Silvertone
Target attributes: Number of Strings
Answer: attribute: number of strings
value: None
source: None