[填空题]
The height, h metres, of ahqcw. ck5d9f; seat on a Ferr1 6i;,5ss9q+* bogsj zjdqhtnis wheel after t minutes is given bysts59i qqoj g*z hs;j+bn16d,
$h(t)=-23.5 \cos (0.4 t)+25, \text { for } t \geq 0 \text {. }$
1. Find the initial height of the seat.
Once a passenger's seat is more than 30 m above the ground, there are no trees in view and they can take unobstructed photographs of a nearby city.
2. Given that passengers only complete one rotation on the Ferris wheel, calculate how long they can take unobstructed photographs of the nearby city.
