The paper shows that, despite a huge number of generated system variants while designing, possible variants set on which to find the best variant can be reduced by thousands of times without the risk to lose the desired optimal variant. This turned out to be possible because the full set of the generated system variants was obtained without taking into account the constraints that are laid down in the requirements of the technical design specification (TDS). A set of possible system variants is obtained by taking into account the restrictions that are specified in the TDS. Here the word "possible variants" should be understood as reflecting the requirements of TDS. So in the work of the authors [1] 10800 system variants are reduced to 24 systems that meet the requirements of TDS.