Point D is between 6 and 8 hours. I don't understand the explanation of point B.

Time of Drying from Drying Curve A solid whose drying curve is represented by Fig. 9.5-1a is to be dried from a free moisture content X1=0.38kgH2O/kg dry solid to X2=0.25kg H2O/kg dry solid. Estimate the time required. To estimate the time required, we need to find the point on the drying curve where the free moisture content reaches X2=0.25kgH2O/kg dry solid. Let's call this point B. Looking at the drying curve, we can see that point B lies between the time intervals of 6 and 8 hours. Since the time interval between each data point is 2 hours, we can estimate that B lies closer to 6 hours than 8 hours. Therefore, the estimated time required for drying from X1=0.38kg H2O/kg dry solid to X2=0.25kgH2O/kg dry solid is approximately 6 hours. Time of Drying from Drying Curve A solid whose drying curve is represented by Fig. 9.5-1a is to be dried from a free moisture content X1=0.38kgH2O/kg dry solid to X2=0.25kg H2O/kg dry solid. Estimate the time required. To estimate the time required, we need to find the point on the drying curve where the free moisture content reaches X2=0.25kgH2O/kg dry solid. Let's call this point B. Looking at the drying curve, we can see that point B lies between the time intervals of 6 and 8 hours. Since the time interval between each data point is 2 hours, we can estimate that B lies closer to 6 hours than 8 hours. Therefore, the estimated time required for drying from X1=0.38kg H2O/kg dry solid to X2=0.25kgH2O/kg dry solid is approximately 6 hours