Answer
$R_{6}$
Work Step by Step
The function is decreasing.
Use the right end points to evaluate the area
$R_{6}$ is an underestimate since it is a bit under the graph.
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.