(a) the momentumen equation is
m * (vt-v0) = f * t
where m = 3.4e5 kg, v0 = 27.3 m/s, f = -4.15e5 N, t = 7.45
so the speed vt= 18.2m/s after 7.45s.
(b)
As the acceleration (a = f/m ) is constant, so
the distance (s) it traveled is that s=0.5*(vt+v0) * t = 169.48 m