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: TroposAir 56" Tornado Oil Rubbed Bronze Industrial Ceiling Fan
Product description: Clean industrial design with three downturned blades that mount at different points on the motor. Available in 316-stainless steel, pure white and oil rubbed bronze
Product feature: Airflow High: 9154 CFM / Watts 79.6 / Efficiency 115, Energy Star Qualified, High Performance Silicon Steel Motor with Triple Capacitor Speed Control, 3-Speed Pull Chain Fan Control and Slide Control for Reverse, Fan Must be Mounted 10' Above Floor Level Due to Metal Blades
Product price: $10.89
Product brand: TroposAir by Dan's Fan City
Target attributes: Number of Blades
Answer: attribute: number of blades
value: three downturned blades
source: product description