Shape of PPC with Constant MRT
The shape of a Production Possibility Curve (PPC) is determined by the Marginal Rate of Transformation (MRT), which represents the rate at which one good must be sacrificed to produce an additional unit of another good while keeping total production constant. When MRT is constant, it means that the opportunity cost of producing one good in terms of the other remains the same regardless of the quantities being produced.

Linear PPC
With a constant MRT, the PPC will appear as a straight line, indicating that resources can be easily reallocated between the two goods without any increase in opportunity cost. This implies that the economy can efficiently produce a combination of goods along this line, maximizing output without any waste.

Efficient Allocation of Resources
A constant MRT signifies that resources are being utilized optimally to produce goods in the most efficient manner possible. The constant slope of the PPC indicates that the economy can easily shift resources between the production of the two goods without any loss in overall output.

No Opportunity Cost Increase
Since the MRT is constant, there is no increase in the opportunity cost of producing one good in terms of the other. This means that the economy can maintain a consistent level of production for both goods without sacrificing more of one for the other.
In conclusion, when the MRT is constant, the PPC takes on a linear shape, indicating efficient resource allocation and no increase in opportunity cost as production levels change. This allows for a smooth and optimal production process in the economy.