This situation can be modeled by a trigonometric equation.

We will use cos.

A is the amplitude; which is 160ft.

is the period.

C is the vertical translation. The centre is now at high.

So

Therefore

To solve D use the info given (at 21secs you are at max height 344ft)

The full equation is therefore:

Q (a)

Substitute into equation for height.

Q (b)

Substitute into equation for height.