The osmotic pressure of a solution of $0.54\ \text{g}$ of a polymer in $180\ \text{mL}$ of solution is $0.15\ \text{kPa}$ at $27\ ^\circ\text{C}$. What is the molar mass of the polymer? Take $R = 8.314\ \text{J K}^{-1}\text{mol}^{-1}$.