If an object is shot upward with an initial velocity, v0 v
0
, in feet per second (ft/s), the velocity, v, in ft/s is given by the formula v=v0−32t
v
=
v
0
−
32
t
, where t is time in seconds. Find the initial velocity of an object if the velocity after 4
4
seconds is 18ft/s
18
⁢
ft
/
s
.