a) a car does an emergency stop from 120000m/s in 3s. what was it's deceleration?

b) what was the car's average velocity and what was the stopping distance?
thank you

v₀= 120000m/s??????????

v=v₀+at
v=0
(a) a= - v₀/t=
(b) v(ave) = (v+v₀)/2 = v₀/2
(c) s=v₀²/2a