Calculates Serum Osmolality and Osmolar gap

Serum Osmolality [mOsm/kg] = (2 * (a) + (b/2.8)) + (c/18) + (d/4.6)
Osmolar Gap [mOsm/kg] = e - (2 * (a) + (b/2.8) + (c/18) + (d/4.6))