The area of region II in Fig 3 with different <i>p</i>₁.

Abstract

<p>There exists <i>P</i> ≈ 1.149 making the smallest area at <i>p</i>₁ = <i>P</i>. When <i>p</i>₁ < <i>P</i>, the area decreases with the increasing <i>p</i>₁; when <i>p</i>₁ > <i>P</i>, the area increases with the increasing <i>p</i>₁.</p