organic chemistry - Comparison of the rate of SN1 and SN2 reaction

It is known that $\mathrm{S_N1}$ (Substitution Nucleophilic Unimolecular) follows the order of rate of reaction:

Tertiary ($3^\circ$) > Secondary ($2^\circ$) > Primary ($1^\circ$)

For $\mathrm{S_N2}$ (Substitution Nucleophilic Bimolecular) the order of rate:

Tertiary ($3^\circ$) < Secondary ($2^\circ$) < Primary ($1^\circ$)

But what is the effective rate of reaction, if we consider that both $\mathrm{S_N1}$ and $\mathrm{S_N2}$ may occur?

Let us assume that we are using $\ce{NaOH(aq)}$ as the reagent, and using n-butyl chloride ($1^\circ$), isobutyl chloride ($2^\circ$), and tert-butyl chloride ($3^\circ$). As water is used, substitution will be favoured, and for this discussion, let us neglect any elimination reaction occurring. In this case, what would be the effective rates of reaction for these cases?