Answer
(a) $40$, $52$
(b) $43$, $49$
Work Step by Step
(a) As indicated in the figure, for a lower estimate, we have:
$A_L=2(1+3+4.3+5.4+6.3)=40$
And for the upper estimate, we have:
$A_U=2(3+4.3+5.4+6.3+7)=52$
(b) For new estimates using ten rectangles in each case, we have:
$A'_L=1(1+2.2+3+3.7+4.3+4.8+5.4+5.7+6.3+6.7)=43$
And for the upper estimate, we have:
$A'_U=1(2.2+3+3.7+4.3+4.8+5.4+5.7+6.3+6.7+7)=49$
