Suppose the accumulated cost of a piece of equipment is \(C(t)\) and the accumulated revenue is \(R(t)\), where both of these are measured in thousands of dollars and \(t\) is the number of years since the piece of equipment was installed. If it is known that

\[C^{\prime}(t)=18 \quad \text { and } \quad R^{\prime}(t)=21 e^{-0.01 t}\]

find the area (to the nearest unit) between the graphs of \(C^{\prime}\) and \(R^{\prime}\). Do not forget that \(t \geq 0\). What do you think this area represents?