capacitor - Impedance load matching

So I've done this so far, and know one of the components is a 50ohm resistor. However I dont know where to go from here. How do i decide if its an inductor or a capacitor?
This is a past paper exam so im aware the other component is a 125nH inductor... but how do i get to that?

Answer

$Z_L=10+\frac{1}{j\omega C}$ turns out 10+j20, well it can't. $\frac{1}{j\omega C} = \frac{-j}{\omega C}$ , so it has to be negative. On the source side the conjugate complex would give a positive imaginary number, so an inductor.

$$Z_L=R_L+\frac{1}{j\omega C_L}=R_L-\frac{j}{\omega C_L}$$ $$Z_L={Z_S}^*$$ $$Z_S=R_L-\frac{1}{j\omega C_L}=R_L+\frac{j}{\omega C_L}$$ $$Z_S=R_S+j\omega L_S$$ $$R_S=R_L , \ \omega L_S=\frac{1}{\omega C_L}$$