Force of friction on two blocks

[afg_91320]

Homework Statement

Two blocks, A and B remain stuck together as they are pulled to the right by a force F = 200 N to the horizontal right. B is on a rough horizontal tabletop (coefficiant of kinetic friction is .800)

a) what is the acceleraton of the system
b) what is the force of friction between the two objects?

pic below:

mass of A = 5.00 kg
mass of B = 10.0 kg

Homework Equations

m A = 5.00 kg
m B = 10.0 kg
F = 200N
kinetic friction = 0.800

The Attempt at a Solution

a) i already found the acceleration to be 5.5 m/s^2

b) this is where i am STUCK. all i have is the coeff of the friction which is .800
what do i do with it??

 

[LowlyPion]

Where is the force directed? On the bottom block?

But that aside, the force of acceleration is just its mass times the acceleration isn't it? And since it's not sliding it must be supplied by friction if the force isn't acting on it directly.

 

[afg_91320]

^the force is directed right towards the middle of A and B coming from the right side.
so mass times accl will give me the force?
that would be 82.5 and i know that is incorrect because the answer for b should be around 173 N