Nelson Corporation produces a part that is used in the manufacture of one of its products. The costs associated with the production of $10,000$ units of this part are as follows:

Direct Materials

Direct Labor

Variable factory overhead

Fixed factory overhead

$$45,000$

$65,000$

$30,000$

$70,000$

Of the fixed factory overhead costs, $$30,000$ are avoidable.

Leslie Company has offered to sell $10,000$ units of the same part to Nielson Corporation for $$18$ per unit. Assuming there is no other use for the facilities, Nielson should

a$.$ Make the part as this would save $$3$ per unit.

b$.$ Buy the part as this would save $$3$ per unit.

c$.$ Buy the part as this would save $$1$ per unit

d$.$ Make the part as this would save $$1$ per unit.