If we were doing a left Riemann sum, we would use the left boundary of each of the subdivisions and the value of the function there to define the height of the rectangle. So this would be doing a left Riemann sum. But we're doing a right Riemann sum. So we use the right boundary of each of these subdivisions to define the height. So our right boundary is when x equals four for this first section. What is f of four? It's eight.