Max power delivered to variable resistor

[enian]

Homework Statement

http://img126.imageshack.us/img126/6400/picex8.jpg"

Determine the maximum power that can be delievered to the varaible resistor R in the circuit of Fig 4.139.

Homework Equations

The Attempt at a Solution

I am not sure how to handle this because the resistor is in that diamond structure. I need to find V thev and R thev Any advice or a hint to get started?

 

[enian]

Okay, so I redrew it to try and get a better perspective but I am questioning where the nodes are in the circuit, do I do as follows? I wonder then how I'm to find resistance.
http://img158.imageshack.us/my.php?image=pic2rc9.jpg

 

[Defennder]

To find R_{th}, short the voltage source. That means drawing a vertical line connecting the blue nodes in your 2nd diagram. Then you must find the equivalent resistance between the red nodes. You have to redraw the circuit in order to solve it easily.

Next to find V_{th}, from the original diagram find the open circuit potential difference across the red nodes with the voltage source added back in. That would be the thevenin voltage. You can use nodal analysis to solve this. I got 30V for this. Once you got both, you can use the formulae for the maximum power theorem to get the answer.