Direction and magnitude of the current

[zooropa]

Homework Statement

Taking R = 1.00 kΩ and ε = 250 V in the figure, determine the direction and magnitude of the current in the horizontal wire between a and e.
http://img5.imageshack.us/img5/7250/img001nkm.th.jpg

Homework Equations

Kirchhoff´s law

The Attempt at a Solution

I must try to apply Kirchhoff´s loop rule to both rules?

 

[Delphi51]

Yes, all three loops. Or perhaps you could combine the 4R and 3R in parallel to get a simpler circuit with only two loops. Once you know I1 and I2, it should be easy to find I in the original circuit.

 

[zooropa]

I think it will be done with 4R and 3R in parallel. But how can i have the value of the new R?

 

[zooropa]

If i have the new value of R i could find I1 and I2, like this:
(xR)I1+(yR)I2=250
and
(xR)I1+(yR)I2=500

I think it will be the solution, but the problem is that i can't find the new value of x and y if i combine the 4R and 3R in parallel to get a simpler circuit with only two loops.
Any help? Thanks

 

[Delphi51]

The 4R and 3R (4000 and 3000 ohms) are in parallel. You must use the formula for the resistance of two resistors in parallel.

I don't understand what your x and y represent.
It seems to me the current through the combined resistors would be I1 + I2, so the equations will each have one more term than you have shown.