A plane from Denver, Colorado, (altitude 1650 meters) flies to Bismark, North Dakota (altitude 550 meters). It travels at $650 \mathrm{km} /$ hour at a constant height of 8000 meters above the line joining Denver and Bismark. Bismark is about $850 \mathrm{km}$ in the direction $60^{\circ}$ north of east from Denver. Find parametric equations describing the plane's motion. Assume the origin is at sea level beneath Denver, that the $x$ -axis points east and the $y$ -axis points north, and that the earth is flat. Measure distances in kilometers and time in hours.