Physic Question: Get Full Explanation

[vle1]

Homework Statement

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Homework Equations

The Attempt at a Solution

This question is confused, I very much appreciate if some one can help. It is NOT a homework question, it was a problem in previous exam. I'd like to have full explanation how to obtain the answer

 

[cristo]

You still need to show some work. what do you know about the topic, what have you tried? I doubt anyone will give you a full solution without you makinig an effort!