The sponsor of a project to move the loan processing system from C++ to the intranet is deciding whether the project should continue or be scrapped. The project has been plagued with issues. So far, \($1M\) has been spent on the project. Of the following, what best describes the \($1M\) that has been spent so far?

a. Opportunity cost

b. Budgeted cost of work performed

c. Sunk cost

d. Phase 1 cost