How do I get these set and get methods to update instead of override the values? For instance, if I set a credit limit of $1500, and then use spendMoney(500) and then use spendMoney(250), I want getCreditBalance to return the running total of $750, but instead getCreditBalance just returns the last amount inputted, 250 in this case.

```
public class CreditCard
{  
 //Source: RR 08/06/14
 private int creditLimit;
 private double spend;
 private double payBalance;
 private double creditBalance;

public CreditCard()
{
  creditLimit = 0;
  creditBalance = 0.0;
  spend = 0.0;
  payBalance = 0.0;
}

public void setCreditLimit(int m)
{
  creditLimit = m;
}

public int getCreditLimit()
{
  return creditLimit;
}

public double spendMoney(double s)
{
  if(spend > creditLimit || spend > creditLimit - creditBalance)
  {
     System.out.println("Credit Limit Exceeded");
  }
  else
  {
     spend = s;
  }
  return spend; 
}

public double payCreditBalance(double pay)
{
  payBalance = pay;
  return payBalance;
}

public double getCreditBalance()
{
  creditBalance = spend - payBalance;
  return creditBalance;
}   
}

```