The volume of a human brain is normally about 1,200cm3. The concentration of solutes in the cerebrospinal fluid (the fluid that surrounds the brain and other parts of the central nervous system) is normally about 300mM.

Estimate how much the brain would swell due to osmosis if the concentration of the cerebrospinal fluid fell to 280mM. In other words, find what the new volume of the brain would be once equilibrium was reestablished. Assume that (i) the cerebrospinal fluid is constantly replenished, so its solute concentration won't change; (ii) only water is passing across the cell membranes into brain cells (not solutes); and (iii) the volume of the brain is mostly water.