The height above the ground h = 18 sin(360t/7) + (18 + 2) where t = time of ride in minutes
h = 26 when 18 sin(360t/7) + 20 = 26
18 sin(360t/7) = 26 - 20 = 6
sin(360t/7) = 6/18 = 0.333…
360t/7 = sin^-1(0.333…) = 18.43
t = 18.43 x 7 / 360 = 0.3585 minutes
The time to turn 180 degrees is 3.5 so the height will drop below 26m after 3.5 - 0.3585 = 3.1415 minutes
The duration above 26 minutes = 3.1415 - 0.3585 = 2.78 minutes
