To those of you who took this exam... there was a question about figuring out the osmolarity of a solution that caused a RBC to swell...the osmolarity of the original solution when RBC was its original size was not given. did you just use normal serum osmolarity of 290, or the sum of serum Na and Cl osmolarity? I couldn't figure this one out, I've been told the answer was 75mM, but with a RBC in normal serum of somewhere between 250 and 300, it would have to swell 4x if the new solution was 75mM...what am i doing wrong??? or was I misinformed about the answer. In the graph it appeared as though the RBC only swelled to max 1.5X it's original size... thanks!