The Blank$\_\_\_\_\_\_$ defines a supervisor as any individual having authority, in the interest of the employer, to hire, transfer, suspend, lay off, recall, promote, discharge, assign, reward or discipline other employees, or responsibility to direct them, or to adjust their grievances, or effectively to recommend such action, if in connection with foregoing the exercise of such authority is not of a merely routine or clerical nature, but requires the use of independent judgment.