A ceramic pottery unit hires 8 craftsmen by paying each of them Rs 900 per day. The 9th craftsman demands Rs 950 per day. If this craftsman is hired then all other craftsmen must be paid Rs 950. The marginal resource (labour) cost of the 9th craftsman is _________.
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 _________________.