I have digital electronics homework that is asking me to design an XOR gate with the following specifications:

Design a 2-input XOR with the following specifications:

R[SUB]L[/SUB] = 1KΩ
V[SUB]DD[/SUB] = 1.8V
V[SUB]OL[/SUB] = 0.1V
V[SUB]OH[/SUB] = 1.7V

However, I don't even know where to start. Could anyone give me a hint? I found this diagram in the book:

 

What does your load look like? Is it 2kΩ ro each supply (giving an effective load of 1kΩ to Vdd/2)?

What do your transistor models look like?