Fischer Company produces a part that has the following costs per unit: Direct material $9 Direct labor 4 Variable overhead 2 Fixed overhead 6 Total $21 London Corporation can provide the part to Fischer for $23 per unit. Fischer Company has determined that 50 percent of its fixed overhead would continue if it purchased the part. However, if Fischer no longer produces the part, it can rent that portion of the plant facilities for $70,000 per year. Fischer Company currently produces 12,000 parts per year. Which alternative is preferable and by what margin