
DP method provides a unified approach to solving all kinds of problems on the replacement.
DP in the model, we consider the process of replacing the nstep, breaking the entire planning period for n periods. Since the beginning of each of these intervals will decide either to maintain the equipment, or its replacement, the management at ku step (£ = 1, ..., n) contains only two alternative variables. Denoted by IP solution, consisting in maintaining old equipment, and a and 3  solution, consisting in replacing old equipment with new. Functional equations, due to two alternative controls on each step, contain only two values: one expresses the conditional earnings (conditional expenditures) in the management of research, the other the same figure in the management of w3. Constrained optimization at each step is to compute the two values and the choice of which the largest (smallest). This greatly simplifies the calculation under constrained optimization, and can solve the problem by hand to replace the large number of steps.
The computational process is constructed as in the previous problem.
Introduction to the condition of the problem functions, evaluating costs, output and cost, depending not only on age t, but also directly from k, that is, the time elapsed since the beginning of the process, is an indirect way to account for technological progress. 