Final answer:
The per unit cost of production in the economy described is $6 (option b).
Step-by-step explanation:
The per unit cost of production in the economy described is $6 (option b).
At an output of 20 units and a cost of $30 for 30 inputs, the cost per unit can be calculated as follows:
Cost per unit = Total cost / Total output = $30 / 20 units = $1.5/unit
Since each unit of input costs $4, the per unit cost of production is $1.5 + $4 = $6/unit.