A. For this case, let us set the variables:
s = 0 (final destination on the ground)
t = unknown
vo = 0
so = 8000 ft
Using the equation, we calculate for t:
0 = -16 t^2 + 0t + 8000
t = 22.36 s
B. For this case:
s = unknown
t = 22.36 s
vo = 600 miles/hr = 880 ft/s
so = 0
Using the equation, we calculate for s:
s = -16*(22.36)^2 + 880*22.36 + 0
s = 11, 677.29 ft = 2.21 miles