Smith Industries Is Considering Replacing a Machine That Is Presently

Smith Industries is considering replacing a machine that is presently used in its production process. The following information is available: $$\begin{array} { | l | r | r | } \hline & \text { Old Machine } & { \begin{array} { c } \text { Replacement } \\\text { Machine }\end{array} } \\\hline \text { Original cost } & \$ 55,000 & \$ 45,000 \\\hline \text { Remaining useful life in years } & 3 & 3 \\\hline \text { Current age in years } & 3 & 0 \\\hline \text { Book value } & \$ 33,000 & \\\hline \text { Current disposal value in cash } & \$ 9,000 & \\\hline \text { Future disposal value in cash (in 5 years) } & \$ 0 & \$ 0 \\\hline \text { Annual cash operating costs } & 8,500 & \$ 3,500\\\hline\end{array}$$
Which of the following amounts represent a sunk cost?

A) $55,000
B) $33,000
C) $9,000
D) $45,000