Explanation

Delta (D) is typically calculated as D = 273 * C / S. For cotton, the critical moisture interval factor (C) is often cited around 80-100 in some texts, but standard agricultural engineering references often list delta for cotton closer to 80 cm or 40 inches depending on the specific crop stage and soil type assumptions used in the source material. However, many standard Pakistani exam keys for this specific question point to 80 cm.