Haemoglobin (Hb) reacts with carbon monoxide according to the equation,

$4\mathrm{Hb}+3\mathrm{CO}⟶{\mathrm{Hb}}_4\left({\mathrm{CO}}_8\right.)$

What is the rate law for this reaction at 20° C?

Trial	[Hb], M	[CO], M	Initial rate of disappearance of Hb $\mathrm{M} {\mathrm{s}}^{-1}$
1	$1.50\times {10}^{-6}$	$1.00\times {10}^{-6}$	$9.20\times {10}^{-7}$
2	$3.00\times {10}^{-6}$	$1.00\times {10}^{-6}$	$1.84\times {10}^{-6}$
3	$3.00\times {10}^{-6}$	$3.00\times {10}^{-6}$	$5.52\times {10}^{-6}$