Can you show us what you have tried please?
Do the following.a = 20
(a) By reading values from the given graph of f, use five rectangles to find a lower estimate and an upper estimate for the area under the given graph of ffrom x = 0 to x = 40.
A ? (upper estimate)
(b) Find new estimates using ten rectangles in each case.
A (lower estimate)
A (upper estimate)