A particle starts at point A on the positive x-axis at time t = 0 and travels along the curve from A to B to C to D, as shown above. The coordinates of the particle's position (x(t), y(t)) are differentiable functions of t, where x′(t)=dxdt=−9cos(πt6)sin(πt+1√2) and y′(t)=dydt is not explicitly given. At time t = 9, the particle reaches its final position at point D on the positive x-axis. The slope of the curve is undefined at point B. At what time t is the particle at point B?