def class_for_time(day, time)
      cfd = self.classes_for_day(day)
      cfd.each { |c| return c if c.time == time }
      nil
    end
def class_for_time(day, time)
      cfd = self.classes_for_day(day)
      cfd.each { |c| return c if c.time == time }
      nil
    end
Returns the class at the given day & time