Determine the poles of this circuit
Use the small signal model of a MOSFET to find the poles.

To use the small signal, you will need the big signal MOSFET calculations (Id, Vds). 

You can find out here:
Small signal models of MOS amplifiers.



With the calculation of Vout, you will find the transfer function involves Cs, Cd and the resistors.

That's how your exercise is done.

Take into consideration that in big signal, the capacitors are useless.

The calculation of gm, the transconductance, is a step you will need.