The binding free energy of a ligand to its receptor protein is $-11.5 \; \text{kJ mol}^{-1}$ at $300 \; \text{K.}$ What is the value of the equilibrium binding constant?

Use $\text{R = 8.314 J mol}^{-1} \text{K}^{-1}.$

1. $0.01$
2. $1.0$
3. $4.6$
4. $100.5$