In our "Wallet" lab, we had a collection of with two instance variables: public class Bill { private int value; Aldollar denomination private String serialNumber; llomitted methods } In class Wallet, we had a display All() method such as this, to display bills in the order entered into a collection "wallet": public void displayAll() Iloriginal version { for(Bill b: wallet) System.out.println(b); } Assume that we will add a call to Collections.sort(wallet) before the loop shown above. You DON'T have to write anything for class Wallet. We want the bills to display in order by value: 1's by serial Number, then 2's by serialNumber, then 5's etc. Example Output: (Bills are displayed by value and by serial Number - exact format unimportant) 1 AA4567 1 AA9483 5 BB2345 5 CC1234 In the space below, write the changes needed in the code for class Bill to allow the sort to work as needed. Just show the changes to the class header and show complete code for any additional methods needed in Bill. [Hint: Use the Comparable interface!]