Orthogonality & Least Squares · Superchallenge problem

Fit a parabola $y = a + bx + cx^2$ by least squares to the five data points $(-2, 2)$, $(-1, 1)$, $(0, 0)$, $(1, 1)$, $(2, 2)$ (samples of $y = |x|$). Find the minimum possible sum of squared residuals.