Estimate the Area Under the Graph Of $f ( x ) = 2 x + 1$

Essay

Estimate the area under the graph of $f ( x ) = 2 x + 1$ from $x = 0$ to $x = 4$ using
(a) four approximating rectangles and right endpoints.
(b) four approximating rectangles and left endpoints.
(c) eight approximating rectangles and right endpoints.