A feed solution with salt solute concentration of $3$ wt$.\%$ is treated by reverse osmosis membrane

purification. The permeate water contains $150ppm($ppm $=$ parts per million by weight$).$

Calculate the retention $R($i$.$e$.,$ salt rejection$)$ and the separation factor ${}_{\frac{w}{s}}($water over salt$).$

Assuming single salt solution in this case. Which of the two parameters, $R$ or ${}_{\frac{w}{s}},$ is better suited

for describing the membrane performance?