Under the current financial constraints, the proposal to increase the police force in City A is not advisable. When calculating the expenditure required to increase the police force, it is not enough to pay the salary of the new police officers, and the payment to the court must also be considered. And the salary of new prison employees, due to the increase in police force brought about by the increase in arrests, sentencing and supervision tasks, it is bound to require related agencies to increase their staff at the same time.
If true, the statement "After increasing the police force, the crime rate in city A will be greatly reduced" would weaken the argument above most.