5 blocks connected together on an incline

[loxo]

Homework Statement

Five blocks are connected together, each with mass m. Two of the five blocks are on an incline of angle θ. What is the acceleration of the last block that is not on the incline. See attached diagram for further details.

Homework Equations

F = ma
F(grav) = mg sin(θ) (on an incline)

The Attempt at a Solution

Broke the componets down in 2 separate parts of those on incline and those off. Attached diagram with details. Not sure if my solution is correct.

 

[mfb]

The result is correct, but I think F_t should point in the opposite direction for blocks 1-3.