Answer:
Relevant cost to make = Direct materials + Direct labor + Variable overhead
Relevant cost to make = $8.60 + $24.60 + $43.00 (1-60%)
Relevant cost to make = $8.60 + $24.60 + $17.20
Relevant cost to make = $50.40
Outside supplier cost ($48.40) < Relevant cost to make ($50.40). So, Factor should choose to buy because the relevent cost is less than outside supplier cost.