The voltage source can be assumed to be ideal and therefore have zero internal impedance .So So you now have a voltage source in series with 100Kohm 100 KΩ.This This can now be replaced with a current source in parallel with 100Kohm100 KΩ. This is just a thevenin nortonThevenin-Norton transform which many textbooks describe .Now Now that everything is in parallel, the Q is easy for you to complete for your homework.