A hand made paper workshop can hire 8 craftsmen by paying them Rs 400 per person per day. The 9th craftsman demands Rs 450 per day. If this craftsman is hired then all other craftsmen must be paid Rs 450. The marginal resource (labour) cost of the 9th craftsman is
_________ is any attribute of the organism (morphological, physiological, behavioural) that enables the organism to survive and reproduce in its habitat.