Unsolved Problem for Equipment Replacement Policy

A company needs to determine the optimal replacement policy for a current $1-$year$-$old machine over the next $4$ years $)=(4.$ The company requires that a $6-$year$-$old machine be replaced. The cost of a new machine is $$100,000.$ The following table gives the data of the problem.

$\backslash$table$[[$Age$,$ :$(v),$Revenue $r(t)($$$),$Operating cost, $c(t)($$$),$Salvage value, $s(t)($$$)$