Let f be the function given by f (x) = sin²(x/4) e⁻ˣ². It is known that ∫₀ⁿ/² f(x) dx 0.0223. If a midpoint Riemann sum with two intervals of equal length is used to approximate ∫₀ⁿ/² f(x) dx, what is the absolute difference between the approximation and ∫₀ⁿ/² f(x) dx?