Answer:
144 feets
Step-by-step explanation:
Look on s(t) like quadratic function. We need to find maximum of the function using 1st diferetioal:
s(t)=-16t^2+64t+80
s’(t)=-32t+64
S’(t)=0 if t=2
For t>2, s’(t)<0
For t<2, s’(t)>0. So the maximum od function is in the point 2.
S(2)=-16*4+64*2+80=-64+128+80=144
