Instruction: Extract the value of the target attribute from the given product information and output it along with the corresponding source.

Input:
Product title: Vivitar VX018-SIL-BXA ViviCam iTwist VX018 Digital Camera with 8x Digital Zoom and 1.8-Inch Flip Screen
Product description: Vivicam VX018 Silver 10.1MP 1.8IN screen 8X DIG zoom 3XAAA
Product feature: 10.1MP still image resolution capture, 1.8" flip screen TFT color LCD, 4x digital zoom, Anti-shake capabilities to combat blur, Built-in memory 16MB SDRAM
Product brand: Vivitar
Target attributes: Optical Zoom
Answer: attribute: optical zoom
value: None
source: None