Royal Company manufactures 24,000 units of part R-3 each year for use on its production line. At this level of activity, the cost per unit for part R-3 is:

Direct materials $ 4.90

Direct labor 7.00

Variable manufacturing overhead 2.20

Fixed manufacturing overhead 9.00

Total cost per part $ 23.10

An outside supplier has offered to sell 24,000 units of part R-3 each year to Royal Company for $41.50 per part. If Royal Company accepts this offer, the
facilities now being used to manufacture part R-3 could be rented to another company at an annual rental of $586,600. However, Royal Company has determined
that $6 of the fixed manufacturing overhead being applied to part R-3 would continue even if part R-3 were purchased from the outside supplier.

I was able to get the first two answers:

What is the total relevant cost of making the product? 997,000

What is the total relevant cost of buying the product? 996,000

I was also able to get the last answer:

How much profits will increase or decrease if the outside supplier’s offer is accepted? Increase by 1,000

I don’t understand how to calculate the opportunity cost.

Here is the question:

What is the opportunity cost of making instead of buying?

Please help me calculate the opportunity cost.