A skateboard halfpipe is being designed for a competition. The halfpipe will be in the shape of a parabola and will be positioned above the ground such that its focus is 40 ft above the ground. Using the ground as the x-axis, where should the base of the halfpipe be positioned? Which equation best describes the equation of the halfpipe? a.) (0, 20); y = 1/80x^2 + 20
b.) (0, 10); y = 1/120x^2 + 10
c.) (0, 20); y = 1/80x^2 - 20
d.) (0, 10); y = 1/120x^2 - 10