Homework 5.1.4 Use finite approximations to estimate the area under the graph of the function f(x) =3 - x - 2x between x = - 3 and x = 1 for each of the following cases. a. Using a lower sum with two rectangles of equal width b. Using a lower sum with four rectangles of equal width c. Using an upper sum with two rectangles of equal width d. Using an upper sum with four rectangles of equal width a. The area under the graph of f(x) using a lower sum with two rectangles of equal width is . (Type an integer or a decimal.) b. The area under the graph of f(x) using a lower sum with four rectangles of equal width is . (Type an integer or a decimal.) c. The area under the graph of f(x) using an upper sum with two rectangles of equal width is (Type an integer or a decimal.) d. The area under the graph of f(x) using an upper sum with four rectangles of equal width is . (Type an integer or a decimal.)