How do I use a button within a movieclip to go to the root?

Question

Hi there, I am new to flash and AS3 and need some help
getting my buttons to work.
I made a script for the file that i am working with that has
buttons located within 2 movieclips. I want that button to load and
image into a UILoader (problemLoader_mc) that I placed on the stage
on the main timeline (the timeline that contains WeekBar_mc). The
problem is that I don't know how to get to the root of the file to
start a new directory to tell my function to load the image i want.
I have tried multiple approaches including:
MovieClip(root).problemLoader_mc.source = problemArray[0]
MovieClip(parent).problemLoader_mc.source = problemArray[0]
root.problemLoader_mc.source = problemArray[0]
parent.problemLoader_mc.source = problemArray[0]
(root as MovieClip).problemLoader_mc.source = problemArray[0]
If anyone can help me out with this, I would greatly
appreciate it, I am banging my head against a wall at the moment.
(Also, please excuse my vague descriptions, I am still learning the
official terms.)
Here is the code that I have written that pertains to this
problem:

Answer 1

I have a mental block for reasoning things out as far as
assigning the listener to an object two mc's away from the main
timeline while having the function in the main timeline, so I may
play with that on my own for awhile. One thing you didn't do
though, was to pay the same attention to the problemArray[0]
assignment in that function, which I assume also lives in the root.
But here's what I'd do for the moment.
Take all that code except the array and plant it in the
timeline where WEEK1btn lives, modifying it as follows....
WEEK1_btn.addEventListener(MouseEvent.CLICK, pload1);
function pload1(event:Event)
MovieClip(this.parent.parent).problemLoader_mc.source =
MovieClip(this.parent.parent).problemArray[0];
I haven't utlized root myself yet, so I am not comfortable
offering you a solution that attempts it.