Both rates are correct only when their scope is visibleBoth rates are correct only when their scope is visible20 boards × (100 × 80 ÷ 645.16) = 248.0005 in²Combined fabrication amount$180≈ $0.726 / in²Same delivered quantity and same outline-area denominatorLess identified fixed charges$120≈ $0.484 / in²Same delivered quantity and same outline-area denominatorEngineering illustration · Illustrative inputs, not factory prices or production commitments