By equation of motion we have v = u + at
 Where u = Initial velocity, v = final velocity, t = time taken and a = acceleration
Here v = 141 m/s, u = 17.7 m/s and t = 6 s
On substitution we will get 
 141 = 17.7+ 6a
 So, a = (141-17.7)/6 = 20. 55 m/

 Aceeleration = 20. 55 m/
 along north direction.