The acceleration would be the net force over the mass. So that would be applied force minus kinetic friction: 23.52N - 13.72N. The force is 9.8N. Divide that by the mass (7Kg) to get an acceleration of 1.4m/s^2.
That's the mistake I made too. The 23.52N is the maximum force that the two blocks can apply on each other, right?
i have provided a solution to this problem is the file that followa..please let me know if there is a flaw in the method or if my handwriting s too cryptic http://www.uploading.com/files/OM9SP8XY/answer.pdf.html
that is a wrong approach, since you have considered forces acting only on the 3 kg mass, its acceleration should 9.8/3 and not 9.8/7...because , in the solution you have considered A and B as two seperate systems and not as one single system of mass 7, A remains at rest wrt to B and B accelerates wrt the earth. There for A would have no net force acting on it wrt B.