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: ESP LTD F-50 with Floyd Rose Electric Guitar Black
Product description: ESP LTD F-50 with Floyd Rose Electric Guitar Black
Product feature: Basswood BodyBolt-on Maple Neck25.5" ScaleRosewood Fingerboard42mm Standard NutThin U Neck Contour24 XJ, FretsESP LH-150 PickupsMaster Volume, Tone and 3-way ToggleChrome HardwareESP TunersFloyd Rose Special Bridge
Product brand: ESP
Target attributes: Number of Strings
Answer: attribute: number of strings
value: None
source: None