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: Oscar Schmidt OD312 12-String Dreadnought Acoustic Guitar Bundle with Instructional DVD, Strings, Pick Card, and Polishing Cloth - Natural
Product description: The OD312 is a dreadnought guitar with a spuce top and mahogany back and sides. The OD312's great action makes it one of the easiest playing 12 strings around.
Product feature: 12-String Select Spruce Top, Mahogany Back & Sides, Decorative Wood Marquetry, Fully Adjustable Truss Rod, Limited Lifetime Warranty
Product brand: Oscar Schmidt
Target attributes: Number of Strings
Answer: attribute: number of strings
value: 12 strings
source: product description
attribute: number of strings
value: 12-string
source: product title
attribute: number of strings
value: 12-string
source: product feature