Answer:
OK draw a diagram - you have the force from (b) acting sown the slope and a component of the weight. Use F=ma to get the deceleration and then use SUVAT. Post your working if this doesn't work.
friction = 900N
braking = 3100N
total = 4000N
w= mxg = 1000*9.81= 9810N
total = 9810 + 4000 = 13810N
force/mass = 13810/1000 = 13.81ms^-2
then using v^2 = u^2 + 2as, i get s as 14 but it is incorrect
Explanation: