Use finite approximation to estimate the area under the graph of f(x) = 5x² and above the graph of f(x) = 0 from X_0 = 0 to x_n, = 4 using i) a lower sum with two rectangles of equal width
ii) a lower sum with four rectangles of equal width
iii) an upper sum with two rectangles of equal width.
iv) an upper sum with four rectangles of equal width​