Using the following Gantt chart: Weeks 1 2 3 4 5 6 7 8 9101112131415161718192021 Activity A B C D E F G H | J K statusline Key: Activity started or complete Schedule ofactivity a. How many \"activities\" are shown? _ ____ b. Which activity (if any) is (are) completed? ______ c. As of SD, which activity (if any) is (are) behind schedule? ______ d. As of SD, which activity (if any) is (are) ahead of schedule? ______