Suppose at) 2 %' (a) The rectangles in the graph on the left illustrate a left endpoint Riemann sum for ax) on the interval 4 S a: g 6. The value of this left endpoint Riemann sum is _ , and it is an overestimate of v Q the area of the region enclosed by y = f(a:), the xaxis, and the vertical lines a: = 4 and a: = 6. (b) The rectangles in the graph on the right illustrate a right endpoint Riemann sum for f(a:) on the interval 4 g :3 g 6. The value of this right endpoint Riemann sum is _ , and it is an underestimate of v @ the area of the region enclosed by y : f(w), the xaxis, and the vertical lines a: : 4 and :1: : 6. HMth'INQ HNUIAUIUINQ Left endpoint Riemann sum Right endpoint Riemann sum