I think that with this problem they assume you are looking at a source like this:
http://users.encs.concordia.ca/~lalopes/Co...rs%20method.pdf
Since that's the exact same circuit (wattmeters on A & C phase with the pressure coils connected to B phase), you can use the formulas in that example.
If they had connected the pressure coils to somewhere else, you'd have to have more information to solve the problem.
I dug in to it a little deeper, and it looks like there are 2 different wattmeter methods. I've been using a different one than presented in that PDF (and different than Kaplan).
Kaplan Method:
(assuming abc rotation, W1 = A phase, W2 = C phase, common PC on B phase)
WA = V I cos (30 + theta)
WC = V I cos (30 - theta)
WA + WC = sqrt(3) V I cos theta
WC - WA = V I sin theta
Method I've been using, same assumptions (Camara, Testmasters, etc):
WA = V I cos (30 - theta)
WC = V I cos (30 + theta)
WA + WC = sqrt(3) V I cos theta
WA - WC = V I sin theta
You don't get a real handle on power factor lead/lag until you get in to the last line there.
I *think* that the NCEES uses the second method (don't have my sample exam with me).
Once again, I think the Kaplan problem doesn't include enough information for us to make an informed decision.
Edit: I have been waiting on our IT department to give me access to a database... meanwhile, I used it to work on Wattmeters even further. I hope you guys don't mind me posting all this crap.
Like my dog with a rawhide bone, I chew on things until they're completely done.
In actuality, I don't solve wattmeter problems like above. I lied a bit...
I solve them using the formula
Wattmeter Reading = V I cos (angle pressure coil - angle current)
Note that if you set your Van reference as 0, your Vab pressure coil angle is 30 degrees for the abc rotation, or -30 degrees in the cba rotation.
Then your current angle for Ia is plain and simple, reference Van as 0.
When you get to the second wattmeter, this is where things get weird.
Your Vcb angle is -(Vbc)'s angle. So if Vab is 30 degrees, Vcb angle is 90 degrees in the abc rotation. Conversely, Vcb angle is -90 degrees in the cba rotation.
Current angle theta for Ic is 120 degrees from Ia, calculated against the phase rotation.
When I use WA - WC = V I sin theta, my power factor angle does come out correct (lead or lag) using this method. Why do I use this method? Because not all wattmeter problems are presented between A&C phases, with the coil on B. I've seen them to neutral, seen A&B phases, etc. I stick with my formula because it allows me to work on any phase.
Having a drawn out phasor diagram for both rotations is the only way I can keep all this junk straight in my head, to be honest.