3 A Ferris wheel at a fairground rotates in a vertical plane. The height above the ground of a seat on the wheel is \(h\) metres at time \(t\) seconds after the seat is at its lowest point.
The height is given by the equation \(h = 15 - 14 \cos ( k t ) ^ { \circ }\), where \(k\) is a positive constant.
- Write down the greatest height of a seat above the ground.
- Write down the least height of a seat above the ground.
- Given that a seat first returns to its lowest point after 150 seconds, calculate the value of \(k\).
- Determine for how long a seat is 20 metres or more above the ground during one complete revolution. Give your answer correct to the nearest tenth of a second.