And each one of these amino acids can basically be any one of those 20 amino acids. So, to carry this out, we have to use a bit of mathematics and probability. So let's begin with amino acid number one. So we have 20 different possibilities for amino acid number one. And so we have 20 possibilities. The same thing is true for amino acid number two, for amino acid number three, for amino acid number four, number five, number six, number seven, number eight, number nine, and number ten.