And we use the left end of the subdivision, the value of the function there to define the height of the rectangle. And once again, you see it is an overestimate. So the left Riemann sum is clearly an overestimate. And it's pretty clear why. This function is, this function never increases. It's either decreasing or it looks like it stays flat at certain points. And so for a function like that, the left edge, the value of the function at the left edge is going to be just as high or higher than any other value, than any other value the function takes on over that interval for the subdivision.