Solution (source code)

= Solution

Adding the equations for the free enzyme and its two complexes gives
$$
\frac d{dt}(e+c_1+c_2)=0.
$$
Thus
$$
\boxed{e(t)+c_1(t)+c_2(t)=e_0}.
$$
This <conservation law> says that the enzyme is neither created nor destroyed: each enzyme molecule is either free, bound in $C_1$, or bound in $C_2$.