now, we know the cannon is on the ground, thus hₒ is 0
we also know the -16, in case you're wondering, that's the gravity acceleration in feet divided by 2
what we dunno is vₒ, or the initial velocity
however, let's use those values given
so, with every passing second, the initial velocity is dropping by 1 foot
after 1 it was 259, then after 2 seconds it became 258
if that continues, after 5 seconds, it'll be 255
so, now if we make t=5 and vₒ=255
then we end up with