Static and Kinetic Friction: Find Force & Acceleration

[phever]

Homework Statement

mA=5kg , mB =10kg , coeff of friction is same for static and kinetic friction = 0.15
g=10ms-2

2 blocks a , b are in contact with each other resting against a rigid wall on a horizontal surface. There is fricition acting between the blocks and the surface . A force of 200N is applied horizontally to A .
a) find reaction forces
b) acceleration if the partition was removed

|_A_||__B__||*-< wall rigid surface

Homework Equations

f=ma , fn=uN

The Attempt at a Solution

since the system is at rest, we assume it has zero acceleration and the reaction force exerted by a on b is 200N and b on wall is 200N .

when wall is removed considering A,B as a system
F=ma
200N - u(Ma+Mb)g = A(Ma+Mb)
200N - 0.15x150 = 15A
200-22.5=15A
177.5=15A
A = 11.84ms-2

please tell me if i have solved the question correctly... some mistake in my method?

 

[pongo38]

A sketch would help clarify the question please.