Answer:
The helicopter still needs to fly up sec 17.0886 at maximum speed.
Explanation:
To find out how far the helicopter went down do 100(seconds) * 10.5 and get 1050
Then how much he traveled back up same thing 150 (seconds) * 5.2 and get 780
Next find the difference 780-1050 and get -270 ft it is negative because it is still BELOW GROUND ( That's how you know if it need to fly up or down)
Last to find how many seconds you need you work backwards so instead of multiplying you do the opposite witch is dividing so you take your feet (270) and divide by the maximum speed (15.8). 270/15.8 is 17.08