Dehydrohalogenation of $2$-bromobutane results in the formation of:

The order of reactivity of the following halides towards $S_{N}1$ reaction is:
$(1) \ (CH_3)_3CBr$
$(2) \ (C_6H_5)_2CHBr$
$(3) \ (C_6H_5)_2C(CH_3)Br$
$(4) \ (CH_3)_2CHBr$
$(5) \ C_2H_5Br$

$CH_3-CH_2-Cl + NaI \xrightarrow{\text{Acetone}} CH_3-CH_2-I + NaCl$ The above reaction is known as $:-$

Toluene $\xrightarrow[{heat}]{{NBS\,/\,CCl_4}} A$ $\xrightarrow{{CH_3ONa}} B,$
The final product $(B)$ formed in the reaction sequence is:

Select the reagent that will yield the greater amount of substitution on reaction with $CH_3CH_2Br$.

Which of the following statements is correct regarding the rate of hydrolysis of the compounds $(A)$ and $(B)$ by $S_N1$ reaction?