acceleration = Velocity changes ÷ time of the velocity changes 
4 m/s^2 =
4 × 10^(-3) × 3600 km / h =
4 × 3.6 =
14.4 km / h
Thus : 
14.4 = V(2) - V(1) / t(2) - t(1) 
14.4 = V(2) - 20 / 10 
Multiply both sides by 10 
10 × 14.4 = 10 × ( V(2) - 20 ) / 10 
144 = V(2) - 20 
Add both sides 20 
144 + 20 = V(2) - 20 + 20
V(2) = 164 Km/h
Thus the final velocity after 10 seconds is 164 Km/h .