A single molecule of haemoglobin, Hb, is able to combine with four molecules of oxygen, as represented by the equation below. $\mathrm{Hb(aq) + 4O_2(aq) \rightleftharpoons Hb(O_2)_4(aq)}$. If the equilibrium concentration of $\mathrm{O_2}$ is $7.6 \times 10^{-6}\,\mathrm{mol\,dm^{-3}}$, and the equilibrium concentrations of Hb and $\mathrm{Hb(O_2)_4}$ are the same, determine the numerical value of $K_c$ for this equilibrium.
- A$3.0 \times 10^{20}$
- B$1.3 \times 10^{5}$
- C$7.6 \times 10^{-6}$
- D$3.3 \times 10^{-21}$