Newton's third law and friction

[cassiek]

Homework Statement

Blocks X and Y are attached to each other by a light rope and can slide along a horizontal, frictionless surface. Block X has a mass of 10kg and block Y has a mass of 5.0kg. An applied force of 36 N

acts on block X.
a) Calculate the action-reaction forces the blocks exert on each other.
b) Suppose the magnitudes of the force of friction on the blocks X and Y are 8.0 N and 4.0 N respectively. Calculate the action-reaction forces the blocks exert on each other.

Homework Equations

Fnet = am (a = acceleration, m = mass, Fnet = net force)

The Attempt at a Solution

I'm kind of lost... I know what Newton's third law states, however, and I understand that - it makes perfect sense. I just am unsure of what variables I need to find and what steps to take to solve this.
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[PhanthomJay]

The action-reaction forces the blocks exert on each other is the rope tension. Calculate it by using your relevant equation, first looking at the system as a whole, and then looking at a free body diagram of each crate.