Suppose that the withdraw$()$ method in the Account class is being tested and there are no other classes implemented. In order to support the test, a stub is needed. What is the class to be replaced by the stub?

public class Account

$\{$

private Audit audit;

public void setAudit$($Audit audit$)$

$\{$

this.audit $=$ audit;

$\}$

public double withdraw $($double amount, double fee$)$

$\{$

if $($amount $>=5000$ && audit.permit$($accountNum$,$ balance$)$;

balance $=$ balance $-$ amount $-$ fee;

return balance;

$\}$

$\}$

Answer: Question $9$