\$V_o/V_s\$ of given circuit
Most of EE are too lazy to solve this circuit the way the @jan did (too much math). 

This circuit can be solved just using the voltage divider equation. Because we have two voltages dividers. 

One at the input (R1 and C) and the second one at the output (L and R2). 

$$\frac{V_O}{V_S} = \frac{\frac{1}{s C}}{R_1 + \frac{1}{s C}}\cdot A \cdot \frac{R_2}{s L + R_2} =\frac{1}{1 +s C R_1} \cdot A \cdot \frac{1}{1 + s\frac{L}{R_2}}$$