The initial cost of one customized machine is $25,000 with an annual operating cost of $5,000, and a life of 6 years. The machine will be worthless and replaced at the end of its life. What is the equivalent annual cost of this machine if the required rate of return is 12 percent and we ignore taxes?

a. $11,081
b. $6,081
c. $4,443
d. $7,593