Finding resistance in a vacuum (triode?)

[Acuben]

Finding resistance in a vacuum (triode??)

Homework Statement

Suppose that we decided to provide the grid bias emf (-8volts) with a grid bias resistor, R(b),
inserted between point B and the cathod. (E(c) is to be removed from the circuit, of course.)
Assume that there is a negleigible current in the grid circuit.
The 25k Ohm load resistor is replaced by a resistor R(a).
If the plate current is still 5.6 mA, what are R(b) and R(a)?
note: it does refer some information from previous problem. There was 8volt battery on
the grid (left part of the circuit) and the current was 5.6 mA (same as here).
R(a) used to be 25k Ohm.
I don't think it matters that much though...
If something from the previous problem needs to be mentioned, let me know.

http://yfrog.com/03vacuumg

answer: (k=1000)
R(a)=23.6k Ohms
R(b)=1.43k Ohms

Homework Equations

load line eq: V=E-IR

The Attempt at a Solution

I really don't know how to set it up in the first place. I spent like 2 hours on this (yes it wasn't a wise decision...^^;;)

I have 1 equation and 2 unknowns...

 

[Acuben]

If you think the problem lacks information, let me know.