Utilizing Lorentz factor;
Lorentz factor = Sqrt (1-u^2/c^2), where u = initial velocity, c = speed of light
But, u/c = 0.960
Therefore,
Lorentz factor = Sqrt (1-0.960^2) = 0.28
For an observer,
t = (Distance to the star*Lorentz factor)/ (u/c) = (14.4*0.28)/0.96 = 4.2 years