6. A particle is located on the x-axis at the point (12, 0). At time t = 0, it begins to move from its starting point in a circle around the origin counterclockwise. It returns to its original location on the x-axis at time t = 6. a. Find a pair of parametric equations x(t) and y(t) which model the location of the particle on the coordinate plane for t 0. b. Find the coordinates of the particle at time t = 3.