Answer
$y_m = 9.00~mm$
Work Step by Step
$y_m$ is the amplitude.
It is given in the question that the amplitude of each wave is $9.00~mm$
$y_m = 9.00~mm$
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.