During the free fall of the object, the decrease in potential energy, at any point in its path, appears as an equal amount of increase in _________________.
7 workers work in a printing press. Each gets paid Rs 450 per day. The 8th worker demands Rs 500 per day. If this worker is hired then all other workers must be paid Rs 500. The marginal resource (labour) cost of the 8th worker is _______.