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A_wall = 2\,(L + W)\,H A_open = \sum_{i=1}^{n} (w_i \cdot h_i) A_ceiling = \begin{cases} L \cdot W & \text{if ceiling included} \\ 0 & \text{otherwise} \end{cases} A_{net} = \max\{0,\; A_{wall} - A_{open} + A_{ceiling} \} A_{wasted} = A_{net} \cdot \left(1 + \frac{p_{waste}}{100}\right) A_{sheet} = s_w \cdot s_l N_{wall} = \left\lceil \frac{\max(0, A_{wall} - A_{open}) \cdot (1 + p_{waste}/100)}{A_{sheet}} \right\rceil \quad N_{ceil} = \left\lceil \frac{A_{ceiling} \cdot (1 + p_{waste}/100)}{A_{sheet}} \right\rceil \quad N_{total} = N_{wall} + N_{ceil} \text{Screws} \approx r_{wall} \cdot (A_{wall} - A_{open}) + r_{ceil} \cdot A_{ceiling}