This problem is easier if you draw a diagram with the ferris wheel and the loading platform.
If you are at 3:00 or 9:00 (horizontal from the axis), you are halfway to the top of the ferris wheel.
If you are at 12:00, you are at the top.
If you are at 6:00, you are at the bottom.
Don't forget to add the height from the ground when necessary.
(a) An easy way to do this is to calculate the heights at 12:00, 3:00, 6:00, and 9:00 and 12:00, and draw a curve through them. Don't forget the platform height. You can double-check that the curve is correct by picking a couple of other points.
(b) Google "equation for height of a ferris wheel". t will be a variable. Remember that it takes 14 minutes to complete a full revolution, which is 360 degrees. The height can be expressed with a sine or cosine function.
(c) You can estimate this by looking at your graph from (a), and calculate the exact answer with the equation from (b).