Let ℝ denote the set of all real numbers. Let aᵢ, bᵢ ∈ ℝ for i ∈ {1, 2, 3}. Define the functions f : ℝ → ℝ, g : ℝ → ℝ, and h : ℝ → ℝ by f(x) = a₁ + 10x + a₂x² + a₃x³ + x⁴, g(x) = b₁ + 3x + b₂x² + b₃x³ + x⁴, h(x) = f(x + 1) − g(x + 2). If f(x) ≠ g(x) for every x ∈ ℝ, then the coefficient of x³ in h(x) is