A tоrоidаl irоn core hаs: Meаn magnetic path length l = 0.5 m Cross-sectional area A = 5 × 10⁻⁴ m² Number of turns N = 200 Relative permeability μ_r = 1000 Permeability of free space μ₀ = 4π × 10⁻⁷ H/m Assume linear magnetic material, no air gap, and negligible leakage and fringing. If the required magnetic flux is Φ = 0.4 mWb, what current I is required in the coil?