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

Input:
Product title: IDMAX12 V.4 D4 - Image Dynamics 12" 1800W Peak Dual 4-Ohm IDMAX V.4 Series Subwoofer
Product description: 1000W 12" ID MAXv4 Series Dual 4 Ohm Subwoofer
Product feature: 12" Dual 4 ohm ID MAX V.4 Series Subwoofer | Pressed paper composite cone woofer | Parabolic EPDM rubber surround | Over 2" long linear excursion | RaDiaToR cooling system for heat dissipation | Radiant Diametric Torsional Reinforcement | High compliance suspension design | Flat spider with NOMEX cloth woven tinsel leads | High-temperature flat wire, flat wound voice coil | Inverted dust cap with logo | Powder coated alloy proprietary basket, Power Handling: RMS: 1200 watts | Recommended Power Range: 300-1200 watts | 3-1/2" peak-to-peak surround excursion, Nominal Impedance (IMP): Dual 4 | DC Resistance (Re): 3.0 | Resonance Frequency (Fs): 27.77 Hz | Equivalent Volume (Vas): 72.16 L | Electrical Q Factor (Qes): 0.73 | Mechanical Q Factor (Qms): 2.98 | Total Q Factor (Qts): 0.58, Frequency response: 20-250 Hz | Peak Excursion (Xmax): 39 mm | Force Factor (BL): 16.68 Tm | Piston Area (Sd): 545.0 cm2 | Sensitivity: 85.20 dB 1w/1m, Sealed Enclosure Suggestion: 1 cu.ft. | Ported Enclosure Suggestion: 1.75 cu.ft. | Displacement: 0.14 cu.ft. | Mounting Depth: 8.15 in | Outside Diameter: 12.40 in | Cutout: 11.02 in
Product price: $13.78
Product brand: Image Dynamics
Target attributes: Impedance
Answer: attribute: impedance
value: 4 ohm
source: product feature
attribute: impedance
value: 4-ohm
source: product title
attribute: impedance
value: 4 ohm
source: product description