Answer:
this app is freakin broken you agree
I believe it is a) 22.4 feet. I looked at the comparison between the 6 feet and the width of the lake and a) seemed to make the most sense.
We can find that the formula is:

We are told that the cannonball reaches its maximum height at t = 4.5 seconds. To find the maximum height, let's just plug this into the formula:

The height is 324 feet. We're done!