To get the egg back to its original size, which is 85 g, the students should take the egg and place it in the vinegar solution. This will ensure that water enter back into the cell moderately within the period of 24 hours. If the egg is placed inside the distilled water, the egg can swell uncontrollably to the point of bursting.
The rationale behind this procedure is that, placing the egg inside the vinegar will increase the concentration of solute inside the cell compare to the water that is outside. This difference in pressure will force water to enter the cell and the shriveled egg will swell back to its original size.