A horizontal force of P kN is applied to a homogeneous body of weight 25 kN, as shown in the figure. The coefficient of friction between the body and the floor is 0.3. Which of the following statements is/are correct?

The total hardness in raw water is 500 milligram per liter as CaCO₃. The total hardness of this raw water, expressed in milligram equivalent per liter, is (Consider the atomic weights of Ca, C, and O as 40 g/mol, 12 g/mol, and 16 g/mol, respectively.)

For wastewater coming from a wood pulping industry, Chemical Oxygen Demand (COD) and 5-day Biochemical Oxygen Demand (BOD₅) were determined. For this wastewater, which of the following statement(s) is/are correct?

Which of the following processes can be used for conversion of salt water into fresh water?