All voltages are referenced to ground unless otherwise noted.
SW1 = CLOSED; VA =
If measurement section in Va has an infinite impedance then when switch SW1 is closed, then the equivalent circuit is
All current transfer from R1(zero ohm switch) and VA = 20.
No current transfer from 6K and 10K branch. and voltage in all point of this branch is 20V.
you can play with meter impedance and switch!