[4 pts] Calcium sulfate (gypsum) is a common scalant of RO processes, especially at high recovery. It has a relatively low water solubility (2.4g/L). A particular feedwater has a concentration of calcium sulfate of 500mg/ liter (common of some waters like the Colorado river). Ignoring concentration polarization and the presence of other salts, at what recovery does the membrane begin to scale? What is the recovery if concentration polarization is taken into account (water flux is 40 liters /m2.hr, mass transfer coefficient is 6.0106m/s, assume rejection is 100% )