1.2 Riemann Sums OPEN I am The rectangles in the graph below illustrate a right endpoint Riemann sum for f(z) = 5 + 2: on the interval [4, 8]. The value of this right endpoint Riemann sum is 82.3 , and this Riemann sum is an underestimate of ~ the area of the region enclosed by y = f(x), the x-axis, and the vertical lines x = 4 and x = S. Right endpoint Riemann sum for y = " + 2x on [4, 8]