Answer
Lower estimate: $-48$
Upper estimate: $88$
Work Step by Step
If f is decreasing, the maximum of each subinterval is at the left end , and the minimum is at the right.
$\begin{array}{lll}
subinterval & minimum & maximum\\
[0,2] & 24 & 32\\
[2,4] & 12 & 24\\
[4,6] & -4 & 12\\
[6,8] & -20 & -4\\
[8,10] & -36 & -20
\end{array}$
Subinterval width: $2.$
Lower estimate:
$[24+12-4-20-36](2)=-48$
Upper estimate:
$[32+24+12-4-20](2)=88$
