I'm having a little trouble with this problem..

so far I've tried using the current through the 400nf capacitor is I=-j/wc=-500j which is by using w=5000.. but not the entire AC voltage is going through that one branch. so i dont know if i'm allowed to approach it that way..

I was also wondering if you were allowed to do it this way:
combine the 2 branches' impedances (but you don't know omega unless you assume its 5000 for all of the elements in the circuit)?


If someone could help me on how to approach this problem I'd really appreciate it. Thank you!

 

Omega is 5000, use this value to calculate the impedance of all the components and then use the voltage divider rule to find the thevenin voltage. Then, using the same values of calculated impedances replace the battery with a short and calculate the impedance seen between a and b.