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: Amigo AM50 Classical Acoustic Guitar
Product description: Amigo Classical Guitar
Product feature: Full size 39" nylon string classical., Solid spruce top., Made in Romania.
Product price: $45.14
Product brand: AMIGO
Target attributes: Guitar Type
Answer: attribute: guitar type
value: classical
source: product title
attribute: guitar type
value: nylon string
source: product feature
attribute: guitar type
value: classical
source: product description
attribute: guitar type
value: classical
source: product feature