at the end of 4 to 7 years of use are those given below. Ignoring taxes and inflation, what is the optimal replacement cycle? Show your work and highlight your final answers. \begin{tabular}{lllll} Number of years of use = & 4 & 5 & 6 & 7 \\ Net salvage value = & $52,000 & $38,000 & $19,000 & $0 \end{tabular}