Which is the domain and range of the parabola with the equation y = 0.5(x2 − 12x − 6)?

a D: (−∞, −21]; R: (−∞, ∞)

b D: [−21, ∞); R: (−∞, ∞)

c D: (−∞, ∞); R: [−21, ∞)

d D: (−∞, ∞); R: (−∞, −21]