Answer
Rate = $k[C_4H_9Br]$
Overall balanced equation: $C_4H_9Br+2H_2O\rightarrow C_4H_9OH+Br^-+H_3O^+$
Intermediates: $C_4H_9^+$ and $C_4H_9OH_2^+$
Work Step by Step
The rate of the reaction is the rate of the slowest step, which is given in the problem.
The overall balanced equation is found by adding the reactions of all 3 elementary steps given in the problem.
The intermediates are the molecules produced and then consumed in the overall reaction. $C_4H_9^+$ is produced in the first elementary step and then consumed in the second while $C_4H_9OH_2^+$ is produced in the second elementary step and then consumed in the third.