Answer:
It is cheaper to make the units in-house by $300,000.-
Explanation:
First, we need to calculate the total avoidable production costs of making 300,000 units:
Total variable cost= 300,000*15= $4,500,000
Total avoidable fixed cost= 800,000 - 200,000= $600,000
Total production cost= $5,100,000
Now, the total differential cost of buying:
Cost of buying= 300,000*18= $5,400,000
It is cheaper to make the units in-house.