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: Ernie Ball 6-string Slinky Nickel Wound Short Scale Bass Set with small ball ends, .020w - .090
Product description: Ernie Ball 6-string Bass Guitar string setsare round-wound for maximum clarity and serious punch. Each string is manufactured with the finest and freshest raw materials in the beautiful Coachella Valley of Southern California.The list of endorsers for Ernie Ball Slinky bass strings reads like a who's who of top selling artists. Strings have small ball ends like guitar strings, not large ball ends used on bass stings. Gauges .020 .030 .042 .054 .074 .090. Part number 2837.
Product feature: Most popular bass string alloy, Well balanced, Good all around sound
Product price: $7.99
Product brand: Ernie Ball
Target attributes: Type
Answer: attribute: type
value: bass
source: product title
attribute: type
value: bass guitar
source: product description
attribute: type
value: bass
source: product feature