I'am practicing circuit analisis about the norton and thevenin's circuits and I can't seem to manage to get the right thevenin's voltage using the node voltage for a)

For the circuit in Fig. 4.111, obtain the Thevenin equivalent as seen from terminals (a) a-b (b) b-c

resolution

1) I did source transformation turning the current source(2A) into a voltage source (10V)

applied node voltage discarding the 1ohm resistance.

I got that Va=18V AND VB=10V

and since vth is in parallel with the 4 ohm resistance then: Vth=(Va-Vb)/4=2 but the solution says that Vth=4

Can you help me get to the desired result.

Your time and attention are deeply appreciated.

Thank you.