Granger Company makes portable DVD players. In its inventory, Granger found $200$ DVD players that had become obsolete. Each DVD player has a cost of $$100.$ Granger can upgrade these DVD players for $$15$ each, after which they can be sold at a price of $$40$ each. Which of all these costs would be a sunk cost?

The original $$100$ cost to make each of the DVD players

The upgrading cost of $$15$ each

The selling price of $$40$ each if upgraded

All of these costs are sunk costs