And each band basically represents a type of protein with a specific type of size, with a specific type of mass. So remember, in SDS polyacryla my gel electrophoresis, the proteins that have a higher mass are higher up, but the proteins that are smaller have a lower mass, lower size, are lower along our gel. Now, in Step A, we basically find that the total protein in milligrams that we're dealing with is 20,000 milligrams. Now, the enzyme activity is 200,000 micromoles per minute, or units. Now, the specific activity will calculate in just a moment. And because this is our original mixture, the yield is 100% and the purification level is one.