Exercise : Date subtractWeeks

• Write an instance method subtractWeeks that will be placed inside the Date class. The method accepts an integer parameter and shifts the date backward by that many weeks. (A week is exactly 7 days.) The date before 1/1 is 12/31.
• Here are some example calls on a given date object:

  Date d = new Date(9, 19);
  d.subtractWeeks(1);    // d is now 9/12
  d.subtractWeeks(2);    // d is now 8/29
  d.subtractWeeks(5);    // d is now 7/25
  d.subtractWeeks(20);   // d is now 3/7
  d.subtractWeeks(110);  // d is now 1/26 (2 years prior)
  

• Test your solution to this problem in Practice-It.