Which of these is an example of an expedited cost?

a$.$ The team completes a major deliverable within the normal $40-$hour work week.

b$.$ New computers are delivered per the agreed dates in the executed purchasing agreement.

c$.$ Production work is halted in the factory due to lack of inventory, and management pays extra for rapid delivery of additional material.

d$.$ Summer months are slow for the company so management establishes summer hours, where everyone gets Friday afternoons off.