Consider the following.

a $=10$

$($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 f from x $=0$ to x $=20.($Round your answers to one decimal place.$)$

lower estimate$$

upper estimate$$

$($b$)$ Find new estimates using ten rectangles in each case. $($Round your answers to one decimal place$)$

lower estimate$$

upper estimate$$