I need help with Forces..?

Question

Heres a crappy diagram of what the problem looks like:
<----[12kg]----[20kg]----[16kg]

Three boxes are tied together and are pulled forward on a frictionless surface by a rope with a tension of Ft=12N.

a) What are all the forces in this problem?

b) which of the boxes will have the greatest acceleartion?

c) Which of the ropes between the boxes will have the largest tension?

Just so you know since the last part of the diagram was cut off it does end with 16kg box

Answer 1

Call the three forces F1, F2, and F3, from left to right.
F1 = 12 N (given)
Since F = ma,
a = F1/(m1 + m2 + m3)
a = 12/(12 + 20 + 16)
a = 12/48 = (1/4) m/s^2
Because the distances between the boxes remain the same, the acceleration on each box is the same, and
F2 = (20 + 16)(1/4)
F2 = 9 N
and
F3 = 16/4 = 4 N