Iridium Corp. has spent $$3\mathrm{.}1$ billion over the past decade developing a satellite$-$based telecommunication system. It is currently trying to decide whether to spend an additional $$349$ million on the project. The firm expects that this outlay will finish the project and will generate cash flow of $$14\mathrm{.}7$ million per year over the next five years. A competitor has offered $$459$ million for the satellites already in orbit. Classify the firm's outlays as sunk costs or opportunity costs, and specify the incremental cash flows.

The $$3\mathrm{.}1$ billion already spent is a sunk cost and it is an irrelevant cassh flow. $($Select from the drop$-$down menus.$)$

a sunk cost