Answer:
Economics is a Science because : like science - it has its practically tested generalisations , theories , laws depicting sound relationship between phenomenas . Eg : Law of Diminishing Marginal Utility , Law of Demand .
Production Possibility Curve is graphical representation of two goods , that can be produced by an economy - given resources & technology .
PPC is Downward Sloping because - If economy wants to increase production of a good, it will have to reduce production of the other , given same resources & technology . It is Concave / Outward bending because - when resources are shifted from production of good in which they are more efficient to the one in which they are less efficient , the Marginal Opportunity Cost (additional sacrifise) increases with each successive shift .
Efficient Points : On the PPC , with best efficient utilisation of resources & technology to produce two goods
Inefficient Points : Below / Under the PPC , denoting innefficient utilisation of resources
Infeasible Points : Above the PPC , cant be reached with given resources & technology unless there is growth in either of the two (resources / tech.)
Effect of a Drought : The PPC will shift leftwards , since the natural calaity has decreased the production potential of economy (both goods) proportionately