5. (7 marks) A steel cable runs from the top of Mont Grand down to the cable car station at the bottom of the valley. A cable car moves along the steel cable. Let y denote the vertical height above the bottom of the valley, and let a denote the horizontal distance from the top of the mountain. (Distances will be measured in metres.) For most of its length, the steel cable satisfies the equation of a hyperbola: Ty - 2, 100. A cable car descends from the top. When it reaches a horizontal distance (z-coordinate) of 60 metres. its horizontal velocity is 12 metres per second. What is the cable car's vertical velocity? (i.e. At what rate is the y-coordinate changing?)