Ranking tension in different crates

[I_LuV_FiZiX]

Homework Statement

Seven crates of various masses are being pulled by ropes to the right, at the same constant speed, as shown below. Assume the ropes are massless, and the coefficient of kinetic friction between crates and floor is the same for all seven crates. Rank the ropes according to the force each exerts on the crate immediately to its left, from largest to smallest. E.g., enter ABCDEFG. If two forces are equal, enter the letters in alphabetical order.

Homework Equations

I can't put the picture itself on here, but I will illustrate it as best as I can. The letters will be enclosed in two dashes to signify the different ropes, and the numbers enclosed in brackets are the masses of the crates.

(1)-C-(2)-B-(3)-A-
(4)-E-(2)-D-
(3)-F-
(6)-G-

The Attempt at a Solution

I am unsure as to whether the force exerted on the crate immediately to the left would be affected in any way by the crates which follow (i.e. for A, B, and D) and I am therefore getting confused. Any help to point me in the right direction would be greatly appreciated, thanks in advance

 

[Hootenanny]

A good place to start would be to consider the forces acting on each crate. What do you know about the sum of the forces on each crate?