Please help with explanation!

1(z) - 32 +4 lesim 21 to 2 3, fast using 4 approxinating rectangles and right endpoints, and then improving your estimate using & approxim A Rectangles - & Rectangles (B) Repeat part (A) using left endpoints. 4 Rectangles = 8 Rectangles = (C) Repeat part (A) using midpoints. 4 Rectangles = 8 Rectangles =(A) Estimate the area under the graph of S(z) = 323+4 from 2 = -1 to r = 3. first using 4 approximationg rectangles and right endpoints, and then improving your estimate using 8 approximationg rectangles and right endports 4 Rectangles = 8 Rectangles = (B) Repeat part (A) using left endpoints