An electron antineutrino is produced at the center of the Sun. Somewhere on its journey to the surface it passes through a region where the density is such that matter effects lead to a resonant enhancement of its oscillations. Estimate the minimum energy required for this to occur if electron neutrino oscillations in vacuo are described by a two-component mixing model with the parameters ∆m²₁₂ = -7.5 × 10^-5 (eV/c²)² and tan² θ₁₂ = 0.444. The electron density at the center of the Sun is approximately N₀ = 3 × 10³¹ m⁻³ and decreases steadily towards the surface.